Russia has 144 million people and a GDP on par with Italy. The EU has 500 million people and - even without NATO and the UK - French nukes, with the ability to develop them in other countries if necessary. Russians aren't stupid, they would never attack us.

Fun fact: Russia has never once invaded Central Europe. Central / West European countries have invaded Russia a few times. Russia does not need space or natural resources and it would be difficult to conquer its way to the soft factors it is missing.

Given the strength of most European countries and their lack of natural resources, the chance of a large war being a net positive for Russia is small. Of course, sometimes there are internal reasons to start a war. Falklands and some US wars and, I think, most of Russia's small wars after the cold war come to mind.

Russia is part of Europe, Russia invading other countries in Europe is presumably a threat those countries would be highly motivated to address. The US keeps forces there and defence commitments because we're afraid of how Europe might act to protect itself if we weren't there, and because we want other countries in the region to feel inclined to accommodate US interests. (In both cases, “Finlandization” is an applicable concept.)