or we can just give China the middle finger when they try to claim their assets.
First of all, most of those assets are not in the USA. They are more likely to be in Africa and Asia, where minerals and oil are produced. What assets do you see in the USA, other than the Treasury debt, that China can even remotely claim?
But more importantly China is a home for many US companies. They have factories there, and those factories are producing top notch products. In case of any hiccup on the international scene all these companies will be for sure seized for debts, and probably sold to Chinese businesses. The USA will be left with no offshore industry, with no money, with no oil, and with no credits for a long, long time. The only resource that the USA will still have is its military, and the nukes. The meaning of the word "diplomacy" may radically change.