China does hold 7% of the U.S. national debt--
-- but for some reason everyone wants to loan the U.S. money (from here) including (believe it or not): Russia $81.7B, Mexico $85.9B, Colombia $37B. and Kazakhstan $24.4B! As far as buying back debt, the way it works is a person (or a government) can borrow from others what ever others are willing to loan, but there's never a limit on how much folks can borrow from themselves. imho it's not really "debt", it's just pretending to have lots of money saved when you actually already spent it.
Isn't that how too many American households do it??
Now....where did I put that picture of the house of cards....?