Don’t be so sure about the Europeans and Brits. Allowing the Russians to move east is a true security threat. They will have high prices and deep economic troubles but nothing like Russians moving east with guns. I’d be surprised if they fold.
I am not saying I am sure about Western politicians, what I am saying is that the people will start trashing everything and the social unrest is what will be the trigger. That or we will all be shipped to fight the Russians. In the UK the energy bills will be going up from around £1800 per year to like £5500 per year from January. And business's energy has not been capped by regulators, so how many of them will go immediately bust? This simply isn't sustainable.