I think the best answer is that China would rather not on account of America attempting sanctions against China. The EU is best not approached by America at this stage of the war.Again, the US and EU combined account for nearly 40% of the global GDP, and if China lost access to this enormous market its economy would grind to a halt, so why would China want to make such an enormous sacrifice to save Russia?
The answer is, it won't.
The wrong answer can't be risked now.
I'm tending toward wondering if America still has enough influence over Europe to bring Europe' countries to bear against China.
But I think that China too could be fearing the question as well.
Your imagined scenario trumps mine in that you have prayer that can be brought to bear on America's behalf!