Well, Biden imo is actually making a smart move by not attacking directly
Currently, he is sending mercenaries in to intervene with the efforts
He can't send in troops directly because of how peace treaties work: if seven countries sign a peace treaty with the united states, and the united states goes to war, so does all of the other seven countries. If the united states sends in troops and Russia decides to try to bring China into the mix, then ww3 will no longer be just a simple meme, but reality