I'm no fan of Putin's Russia, but let's be realistic here. Russia is not a military threat to Europe. The EU countries, if they wished to, could be well ahead of Russia, both economically and militarily.
Okay, Russia has lots of nukes. But they have never used them, and have never even threatened to.
Putin thinks he is the protector of ethnic Russians everywhere. So Crimea, yes. And he would probably make a move on the Baltics if the opportunity arose. Beyond that, he has no interest.
In the face of this relatively minor threat, then, I see little reason why Europe should not be providing its own defense, and the US troops should be brought home. European industrial and economic power should be way beyond what is needed to see off Russia. Euros are always banging on about their superior culture and lifestyle, while characterizing Americans as gun toting redneck Jesus freaks. We should leave them to it.
Perhaps Trump'll get this done soon, too!