Except that there are obvious downsides for China:

1. It would push the USD down, delivering losses on their investments and making Chinese imports more expensive


2. It would invite US retaliation; indeed if the USA was unable to finance its trade deficit it would have to reduce imports and/or see the USD continue to weaken 


3. The Chinese would have to find other homes for their huge trade surpluses - as well as any money they pull out

So, yes, a dangerous game - but almost certainly more so for China.

One can't help feeling this will all accelerate the  crumbling of the  world trade edifice - it wasn't looking too good before all this.  If Trump gets another term I think we are going to see fundamental changes and probably even if he isn't.  Lots of people and countries are pretty hacked off with China just now.

The US and China are 2 bookends in the current set up, both are likely to suffer from its demise, not just China.