The US is insane if they actually consider this. Cutting Russia off from the global financial system is one thing (and it already had a huge impact) but China? The largest trading partner of virtually all countries on earth?
China will say: to keep trading with us you need to use our system now, and before you know it you have a largely dedollarized world. Done.
Also what would be the pretext for this? Because China keeps trading with Russia, just like 80%+ of the countries in the world do? How will these countries react when they see the US goes for crazy imperialistic moves like this? The natural and sane reaction will be to ask "how do we de-risk ourselves from this so they can't do the same to us?"...