When people park their money on bonds, they are not buying up stock, which is used to generate capital growth for the businesses and the economy. This is how the government competes with the private sector in a not so beneficial way.
Just concentrate onto this single point, it showing the dynamism of the "treasury dumping".
First of all, your reasoning ( and this is the basis of the later logical construct) is that there is a finite amount of money chasing investment opportunities, and if there is a mismatch between the two then the interest rate adjust.
So, it was true during the gold backed money, and it is true for say the bitcoin, but otherwise it is a wrong interpretation of the current monetary system.
Actually ,this was the reason of the abolishment of the gold backed money.
The level of money depending solely on the amount of profitable investment. The central bank can issue as much loan as the retail/investment banks wants.
Best example is the current monetary system of USA, Japan since 1990, and generally all war economy in the past.
You have to falsify the above statement to be able to spell doom to the US if China stop to buy / dump treasuries.
So, if say China decide to sell the treasuries then the US central bank can adjust with the interest rate the inflation, and the absorption of the bonds.
The other way should be the discount on the bonds, that is defamatory, so the central bank will avoid that.
So, China will receive a lot of dollars for it bonds, that will have 0 interest, compared to the positive interest of bonds, and both of them will have negative interest compared to the inflation.
So, in short notice china will loose best part (up to 99%) of its investment value in treasuries.
Of course there will be inflation in the USA, and huge demand for workers,and so on, and the dollar will worth way less compared to the yuan than now, but the world trade and monetary system won't be the same like today. But it will be more positive than negative to the USA.