Yea im not sure how a civil war in the United States would affect me as an European... It certainly would, but I'd survive. Isn't the whole point of apocalyptic events to not survive them?
Europe would curb stomp Russia in a conventional war even without the US.
Ten times the GDP, three times the population and our military stuff mostly works, Ukraine has done a phenomenal job with what they had but Russia turned out to be even more of a Basket case than expected.
The problem is how much damage they can do before we put them back in their box and whether getting the shit kicked out of them would triggger a nuclear exchange which would get really out of hand.