People seem to forget....
Russia and the US are neighbors separated by maybe 10 miles of ocean.
Both have huge nuclear arsenals and other weapons of mass destruction. Even trying to Nuke them would result in both Canada and the US getting the fallout from such an attack.
There are peaceful resolutions to this conflict but Ukraine and especially Russia didn't want to. Russia tried to be a bully with its desires but now is stuck trying to back up their claims. (Bullying is How they control their neighbors)
So if we even tried to begin a troop and equipment buildup of that sort it would instantly cause Russia and PRC to fire off its nukes like cornered animals.
Now in truth we have no quarrel with Russian people themselves...just their government. And now that most of their military personnel are conscripts...we really don't want to hurt them either....they are just pawns in this battle. Their only desire is to just survive this mess. The Russian soldiers could care less about Ukraine and its stuff. (They are thought of by the Russians as stupid farmers without manners and marrying their cousins too often)
But if Russia pulls out without some sort of a "win" they will have lost much of their bullying power in the area. And that is not a good thing either.