The US does not need to sell Treasuries to fund itself.
It doesn't matter how much China (or anyone else) owns or buys.
It gives them no power over us. Having Biden as a puppet does, but not owning Ts.
At the current, and foreseeable, rates of spending and taxation the loss of ability to sell Treasuries would cripple the government and tank the economy. Which, as long as that remains the case, gives large foreign buyers of our debts substantial influence over our policies and affairs.
Unfortunately it’s not like changing that with a snap of the fingers is without major problems. While ripping off that bandaid might be the best long term tactic, the short term upheaval makes that political suicide. Best we could hope for would be a lengthy process of spending stasis and letting the economy grow to the point that we had surpluses sufficient to actually retire large amounts of the debt.
The alternative is hyperinflation such that a typical house would cost billions.
Or collapse, civil war, and descent into tyranny.