> But 44% of US corporate sales happens overseas. A shutdown of global trade would be quite bad for the Chinese, but it would be worse for the "richest nation on earth".

You're wrong about that. You're talking about the S&P 500, not all US businesses (most US businesses have very little overseas exposure in fact). China is a modest fraction of that S&P 500 44% figure. Further, as noted previously, the US doesn't benefit from or require global trade nearly as much as China (which is also highly dependent on an inflow of dollars to fund its economy).

China currently has a serious dollar based debt problem with its corporations. The Chinese economy requires constant, large inflows of USD. The US is the exact opposite, it has almost no foreign currency debt dependency. And it has zero dependency on the Yuan.

The US is highly self contained in all regards, including its wealth. Its sole major weakness is the consumer junk that people buy at Walmart, mostly from China. Fortunately, the US can replace China with three dozen other countries that would love to start making those easy-to-replace goods, like $60 microwaves (which can easily be made in Mexico or Vietnam). This trade & manufacturing shift is happening right now and will continue.

> China would aggressively dump US treasuries.

Which would do almost nothing. China represents a now trivial part of the US debt picture. Each year that goes by that position becomes ever less important. The Fed could very easily replace China's holdings with a round of QE. The US isn't lacking for demand on its debt, especially while $13 trillion in global debt yields nothing.

> China stops exporting rare earths that even the US military depends on.

The US has begun the process of using the Defense Production Act, which enables the US military to spend money and allocate resources to fix this problem as it sees fit. China has maybe a year to utilize rare earths to any impact, after that it's likely to be permanently removed as a trade weapon. China already made a mistake by hinting at rare earths as a weapon, the US is going to preemptively correct the issue.

Rare earths are plentiful and the US has two domestic mines capable of production near-term (one of which is active right now). There are multiple domestic processing facilities set to be built in the next couple of years. The US military will begin expediting all of that. It wouldn't take more than a year if it were necessary. Further, it's only a small subset of rare earths that the US has a strong need for, narrowing the problem considerably.

Rare earths is among China's least potent threats against the US. If they make the mistake of trying to use it, the US will permanently break their hold over that market (something that Japan almost single-handedly accomplished previously, while having a far smaller economy and far less ability to force outcomes than the US; the US would smash China's global rare earth market share, it would only take a few billion dollars in annual spending for a few years by the US military to do that; an easy move on a national security basis).

> Chinese nationals are forced to sell their holdings in the US.

That would hurt China and benefit the US. It would be ideal for asset prices in the US to decline slightly (they're extremely high right now). Regardless, Chinese nationals do not hold enough US assets to substantially impact US asset valuations.

> All of these things would cause a major financial crisis in the US

None of those would have any serious impact at all.

> China also is not as dependent on fossil fuels, due to extensive rail links between their major cities.

China's demand for oil is increasing, not declining. Their overall power production from coal is increasing, not declining. They've merely been simultaneously increasing their share of renewables. Over the last ten years their oil demand has increased by 50%. They're currently consuming roughly as much coal as all the rest of the world combined.

It makes them exceptionally vulnerable to an external energy shock from fossil fuels. They're incapable of meeting their own energy supply needs in the next 30 years.