The US doesn't give a shit about Ukraine.

If the US government really gave even a solitary mummified fuck about Russia's invasion of Ukraine, they would simply send a black ops team in to Russia to assassinate Putin like they did to Bin Laden and to dozens of rightfully elected leaders around the world in their quest for oil. The fact that they've just been letting him carry on means they either stand to benefit somehow, or for some reason they just don't care.