If the KSA "decoupled" from the U.S. the families in the Kingdom of Saudi Arabia would end up with their heads on spikes in no time. That's the harsh truth of it and they know it. So they're threatening breaking up with the U.S. They have some leverage because even if the U.S. doesn't buy as much of their oil it doesn't want its enemies to get it (and it has corporate interests). Which is why Biden humiliated himself. It's complicated! But in the end, the KSA doesn't have the military strength to protect itself so there's only so much playing of U.S. and China against each other it can do before the U.S. protects its interests--not pretty stuff.

China just wants the oil. So as long as those interests aren't threatened it doesn't care what happens in the KSA.

My 2-cents. When MBS killed Khashoggi He burnt a get-out-of-jail-free card which I predict will haunt him down the line. He's trying to play tough. Will it work? Interesting stuff.