Russia is an even smaller economy than the US, and even then many countries continue to trade with them despite their aggression.
Sanctions hurt everyone involved. If China stopped trading with the US, their economy would tank too.
Furthermore, there are ways around sanctions.
The US is much more self-sufficient than Russia.
It is not hard to comprehend, but it is also not a surefire way to deter an invasion.
And of course remember that not all actors on the stage will behave "rationally"... US leadership especially.
