Perhaps some of your difficulty in understanding what is going on is that you are ascribing "the US" and "China" as real entities capable of action or intent. In fact they are labels that real individuals and actors capable of action use as shields for various purposes. This is well discussed by e.g. Buckinminster Fuller's books describing "England".
I agree with you, USA China are two huge, heavy balls rolling down their trajectory and nobody, not one person can make change to it. Because they are both too big, way to big.
I always think a safe world should divide USA and China into smaller countries. My thinking will make myself a criminal in both countries.