This is very wrong. Anything is possible, it's just a matter of political will.
The most likely scenario is russia is pushed to the brink and collapses internally like 1917 and 1990. Then Russia balkanizes along ethnic lines, like 1917 and 1990.
The world today would be a much safer place if 1990 Russia had split into about six independent states, each comparable to Kazakhstan or Ukraine. Hopefully that will eventually happen when Putin is gone. Imperial Russia should cease to exist like imperial Austria did. It has been a great source of misery throughout the centuries.
I don't think many people are actually nationalistic zealots who want to eliminate other countries so long as theirs is technically still existent, as even a king of ashes won't have a great life compared to a mid-range billionaire today.
I'm not alone in believing that this alone is reason enough to risk everything. A threat to freedom anywhere is a threat to freedom everywhere.
This is flatly wrong and gives far too much credit to Europe. The US had to shake Europe and Ukraine awake to the impending invasion of Ukraine. And I say this as an EU citizen.
And it's not like Europe isn't fighting back. European intelligence has been deep inside Russian networks since before the first invasion of Ukraine. From the European side, the invasion of Ukraine is a proxy war, with billions of euros spent on fighting Russia, while to Russia the war is a normal invasion with Russian (and now North Korean) troops on the ground.
The way Europe (except for Ukraine, of course) is fighting Russia mostly benefits Europe, as far as I can tell. Most of Europe's losses, so far, have been economical. Switching to a war economy to defend against Russia would probably cost more and be less effective. Until Ukraine falls, I don't see why Europe would want to change that deal.