Good points.
The Chinese ARE in trouble, as you stated. The question is, who will they invade? Pakistan? Vietnam? Taiwan? At this point, who can tell? And if they set their sights on a US ally, will our then-President have the courage to confront them?
I think the real question is, "Would it be worth it for us to confront them?"
If Russia gets into a cash crunch, the Chinese could offer to use their cash reserves to buy the resource-rich areas of Siberia.
They are less likely to invade India, a country with their own nukes. They might do something with Pakistan's northern tribal regions. They would most like to do something with Taiwan.