Interesting that US 10 year Treasury Bond yields have tumbled from 4.8% in January to 3.95% currently, which saves the US taxpayer hundreds of millions in interest payments on America's massive debt pile of around $36.5 trillion.
The biggest drop has happened in the last week from 4.4%, probably as investors have dumped stocks and moved into 'safe haven' bonds instead.
That's not how bonds work. A 10y bond is sold by the govt with the promise it will pay a fixed amount of interest for 10 years. The amount of interest it pays on a bond is fixed - it does not go up or down with the markets, so it won't "save the US taxpayer hundreds of millions in interest payments on America's massive debt pile of around $36.5 trillion". Bonds already issued have to be paid at the issue rate.
As the owner of such a bond, you can sell it on for whatever they want. Say you paid $1 for the bond, and the govt promise to pay 10cents per year interest - effectively a 10% interest rate. If you sell it to a new owner, then the 10cents interest will be paid to the new owner. At the end of the 10 years the govt will pay the current owner their $1 back. It will therefore have cost the US treasury $2 to borrow $1 for 10 years.
If during the bond period you sell it to someone else for less than you paid (say 90 cents), the new owner will still receive the promised 10 cents interest, so the new owner effectively sees 11.1% interest, but the govt is still only paying out 10 cents. Similarly if you sell it for more than you paid (say $1.1) the new owner still receives the 10 cents interest, so the new owner effectively sees 9.09% interest, but the govt is still only paying out 10 cents.
The only time the govt is really bothered about the bond rate is if/when they are trying to sell NEW bonds. If you crash your economy then buyers of new bonds are going to want more interest before agreeing to give the govt any more money. The bond rate can therefore be seen as a measure of investor confidence in the countries economy.
The fact China holds huge amounts of US bonds is a problem for China, not the US, providing the US can continue to pay the initially agreed interest (which it always can by just printing money if required).