Russian economy is weak, agreed, but militarily they are still the only significant threat to US global dominance. China's military is much weaker in comparison.
China is a vastly bigger consideration. If China decides to invade Taiwan the US could lose access to most semiconductors. China’s military is developing rapidly.
If Russia were so inclined (I don't think they are and don't see why they would be) they could turn the Island of Taiwan into a pile of gravel on the floor of the China Sea. They have several thousand nuclear warheads with the means to deliver them; more than enough to overwhelm any extant ABM system.
For that reason if for no other, I think an American conflict with China is more likely than a conflict with Russia. China still has hundreds of nukes too, which is hundreds too many, but that's many times less than what Russia has.
To be clear, a direct war between any three of these countries would be a stupid, horrible idea.
