US Fed can print dollars and buy all their own bonds as long as they can get the rest of the world to use dollars for trade and investment payments. They basically export their inflation to the world.
China should accelerate using yuan for trade, investment and financing. Open domestic yuan-denominated bond market to foreigners so they can buy yuan-denominated government bonds after using yuan for trade and investment payments. Weakening the dollar payment system is the key to weakening the US empire.