Those are worthless pieces of paper (our US dollar) only if the USA plans on defaulting on all the US Treasuries those nations have also bought. China has piled up a lot of worthless pieces of papers so is now able to exert more control over us. Obama bowed down to Hu Jun Tao last time they met
If you owe $400,000 worthless pieces of paper to your creditors do you plan on screwing them via a default?
That's something you might want to consider if it's the last day of your life and you have no heirs!