Well, IMHO dead Russians are vastly preferable to dead Americans especially if we have no strategic interest in being in Syria and Russia does. Russia is not the Hegemonic power the USSR was. They have an economy the size of France and as Trump has shown us the major power battles of the 21st century will be economic. What does Russia really want other than a Med port? To suckle at Uncle Sugar’s teat like the rest of the world. Granted, Putin is ex-KGB so is a sneaky SOB. It also makes him smart. There is nothing for us in Syria. There is something for him. Let him have it. It brings our troops home.
So long as Hezbollah exists we have a bone to pick.