If China dumps the U. S. Treasury bonds to fast it may take China down too. China wants to make the U. S. Dollar more valuable so it can sell more product to us. It will not be good for us to have a strong dollar right now. It would make U. S. product more expensive to buy and we may lose more jobs.
For China they will get more time to become a supper power and will take the U. S. down slowly to a collapse.
I still think China wants to become the world power but needs to do it right. They know that when the U. S. goes into a collapse the collapse may take them with it so they are planning for it. They have a way to make the U. S. Dollar stronger for a time, after the sell there U. S. Treasury Bonds then they do not have the any way to pull the dollar up anymore.