Obviously we can go around and around on this quite a bit because it's mostly theoretical. The actual information that would be needed to resolve this is likely highly classified and I don't have access to that sort of information any more. The other problem being that even if one could get access to the appropriately classified information that STILL doesn't guarantee either its accuracy or the accuracy of estimates based on it. That being said:
1) Yep, the U.S. economy in the tank would end up meaning the rest of the world's economy would end up in the tank just like a row of falling dominoes. However, let it simply be observed that desperate times call for desperate measures and it could be argued that our economy is actually more vulnerable in some ways to long term disruptions than the economies of some of the other countries out there. For one thing we just about don't have a manufacturing base anymore.
4) I don't doubt that the Japanese loathe the Chinese and the Russians. However, the Japanese are pragmatists and as you have so cogently pointed out they don't have an army anymore. Their navy, while very well equipped and highly professional, is also too small to seriously butt heads with a combined Sino/Soviet fleet. By the way that is my professional opinion after having seen them in operation (*). Given a scenario where America is unable to provide them with enough of a security blanket to protect them from the Chinese and Soviets operating in what is almost literally their backyard I could see Japan deciding that Finlandization had a lot going for it. This would be a much more telling argument in the hypothetical scenario discussed where China had already scarfed Taiwan and the U.S. Navy had taken a serious hit.
5) When I talked with some of my counterparts in the RAN over a decade or so ago they weren't looking at Indonesia as a laughing matter. It's not really "power projection" if you're talking about something a country is doing in its own back yard. Australia is for all intents and purposes in Indonesia's back yard. The RAN is basically in the same condition that the Japanese Navy is. Well equipped, highly trained, thoroughly professional, and entirely too small to accomplish much more than dying gloriously for their country if they get hit hard enough and fast enough.
At one point in time I was able to have a long discussion via email with a gentleman who was in Australia's equivalent of the GAO. He told me that the Royal Australian Army's plan for the defense of Australia against an invading force was to abandon the coast and wage guerilla war from the Outback. My comment to him was that if they weren't planning on holding at least one of their port cities it would make attempting to give them aid and comfort almost impossible.
Granted I haven't stayed current on affairs in Indonesia. However, one good strongman dictator can occasionally turn things around in a country in a surprisingly short period of time. Australia has a lot of coastline to cover, not that many ships to do it with, and could be faced with the potential problem of having their navy taken out by virtue of having the ports it operates from being overrun.
6) You will notice my scenario had the Sino/Soviet force stopping to consolidate their position before they proceeded on into CONUS, with a supposition that said period of consolidation could last several years. Need I say more?
7) The Juan de Fuca straits that one has to be able to get in and out of in order to access Seattle are a lot more constricted than the areas around the other ports on the west coast that the Navy could use. This would be especially true if there was a hostile, foreign power occupying Vancouver Island. They wouldn't NEED to take either Seattle or Bremerton in order to control the flow of ships and cargoes into and out of the ports there.
At any rate, I think I've commented enough. I was mainly trying to make the original scenario that was proposed more "realistic" than it was originally. I think I succeeded, though other people may rightly disagree. If I were to get out my crystal ball and prognosticate what the actual "real world" scenario is likely to look like some time in the indefinite future I think we would see.
A) An economic collapse. Based on the way that I understand things this is a question of when, not if, and it will be nasty.
B) Unrest for various reasons at least in urban population centers here in America. Reasons could be as varied as the Reconquista types making their move, or hordes of people reacting very badly to loss of government provided benefits and other problems associated with the collapse. Expect that the government here will react to this by becoming MUCH more totalitarian, which will in turn set off a whole host of other consequences.
C) In fact, regardless of whatever else happens here, I see the government as becoming MUCH more totalitarian. History repeats itself, but each time the price goes up.
D) As a result of A, and definitely if we are dealing with A & B, I see various different groups on the world stage making various different plays. China has wanted Taiwan so badly for so long I think it is inevitable that they will do something to take it.
E) If things do go badly enough for long enough here in America, I think we might see some sort of foreign intervention/involvement. Quite simply the stakes would be too high and too tempting to expect that everybody else would simply sit off to the side and let America get its act together. The least we could expect is that somebody would play games with various special operations forces here. Arguably judging by real world news items dealing with alleged Mexican troops playing games on our southern border and Chinese dissidents being assaulted and robbed in their houses here in America that may already be happening to some extent. Things could get very interesting.
As for US involvement in Taiwan, I think that this is the crux of the matter in my timeline. US has never had a very clear policy concerning Taiwan vs. China, and if the reunification seemed to be coming from within Taiwan...
For that matter, I set up the Taiwan incident as the reason China wants to invade in the first place: the US was too threatening during the takeover, and hit China with tariffs after the takeover, giving both the military and civilian leaders a reason to invade.
Cutlass, I enjoyed reading your general timeline, and I thought it was interesting how you tackled it from a different perspective. I'm not sure, however, that the Russians would be that terrible a threat (unless you plan on setting it in the Cold War era...), so I'm not confident such a boldly militarist plan would work (which is why my timeline relied more on stealth). Still, I do understand that the economic hit we would take in your timeline would significantly reduce our own military power.
Baator of the dark, I'm not sure that you understand, but for many of us, working out the plausibility is fun. Now you brought up several good points (especially Operational security), but I have to say that many of them have already been discussed and (some) dealt with. So I, and I think the rest of the posters, would appreciate it if instead of attempting to kill our topic, that you contribute thoughtfully to it.
-MVK
IMHO the only hope China or Russia or both of them acting together would really have of conventionally invading the U.S. with large forces would be to come over the Bering Strait route. The reasons for that are twofold:
1) Assuming the U.S. Navy is still at least marginally functional they aren't going to be able to ship the supplies that they will need through any other route that I can think of.
2) The Bering Strait is potentially confined enough that they could achieve and maintain a local naval superiority that would enable them to get their logistics shipments set up through there.
Modern military forces are the biggest logistics hogs that have ever existed in all of recorded history. In order to have a reasonable chance of taking over the North American continent, or even a significant chunk of it, you would need millions of troops and tens of millions of tons of supplies. Logistics hassles of that magnitude are basically only going to be solved by shipping and rail lines.
Now, how likely is it that China and Russia would get along well enough to pull that sort of thing off? Probably not very. But, if you want to have a scenario going where China is invading the U.S. with even a reasonable chance of success then they've got to be able to get their main military formations here en mass. To my way of thinking that necessarily implies using the Bering Strait route, which almost automatically assumes that China and Russia would have to be getting along in some fashion to pull that off.
That is also why I have the economic collapse and the Taiwan issue with large U.S. Naval losses occurring first. The U.S. Navy pretty much reigns supreme in the open ocean. Once you get up close to the coast it can be a different ball game and today's modern navy can have some serious disadvantages trying to operate too close in to a hostile shore.
So, take our economy into the toilet, remove a relatively significant chunk of the U.S. Navy assets available in WESTPAC, and then a combined Sino/Soviet fleet just might be able to maintain that local naval superiority in the Bering Strait they'd need to make the invasion work. But without all that, I just couldn't suspend my disbelief enough to see it happening.
The Chinese could potentially get an initial assault force in position using some type of subterfuge. However, once they have actually come into the open and made the assault, seizing a port or two or whatever, the jig is up. You can bet your bottom dollar the Navy would try to intercept any and all shipping that looked like it was going to a port that was under the control of an invading hostile force.
In a nutshell, you can't have serious heavy-duty military activity going for extended periods of time without serious heavy duty supplies. As I commented earlier, the Chinese would literally have to get millions of troops involved and that would necessitate tens of millions of tons worth of supplies they would need. Only two ways to move that much junk, by sea or by rail. There are no rail connections between China and the U.S. that I am aware of. The freighters with the supplies have to come to a port, and to do the Chinese much good they've got to go to a port the Chinese control.
Now, as to the Chinese playing games with Mexican and South American allies helping them, that is a more serious scenario. I don't know how closely if at all our intelligence types are monitoring what is going on in Mexico. So, assume that if the Chinese are willing to use a significant amount of subterfuge they probably could get a rather large force pouncing on into the U.S. through a border that is basically defenseless.
However, you come back to the base problem that eventually those troops are going to need supplies, which are going to have to come from somewhere. Unless Mexico is able to manufacture all the needed supplies on their soil they will have to import those supplies, which brings us back to the Navy intercepting freighters and blockading ports under the control of hostile nations.
Also, that is one of the scenarios where American Militia units could end up playing a significant role using hit and run tactics against anything that looked like a hostile supply column.
There is an old board game I have which may or may not still be available or findable. The title of the game is "SS Amerika". It was copyrighted in 1990 and published by 3W, Inc. in Cambria, California. You will just about need a full sheet of plywood to lay the board out and set up all the pieces and relevant charts on. It is an operational level simulation of hypothetical Axis invasions of the North American continent during World War II. The map covers the entire continent from north of the Yukon river all the way down to South America below Medellin, Colombia.
While it obviously has nothing at all to do with the Chinese, if you can find it and play it you should get an excellent idea of just how hard it could be to actually pull off a successful invasion of an entire continent. The biggest problem any attacker ends up facing is the force to space ratio that he would need to try to control the entire area given no popular support. Basically, regardless of where he goes and how he does it he's going to end up spread too thin. And that's not even counting what we could scrape up in terms of functioning military units on short notice.
Any successful invasion of the continent would necessarily take decades and probably end up looking more like the 30 and 100 years wars that ravaged Europe several centuries ago. Not a pretty sight.