I've avoided saying this because any comparison with Nazi Germany tends to come across as hyperbole, but I see many comparisons between Russia today and Germany in the 1930s, and between Putin today and Hitler. I am not talking about gassing Jews. The comparisons that I see are: formerly powerful country that lost a major conflict and lost much of its power, influence and pride; a leader who greatly resents this loss and plays on his people's sense of humiliation and pride to become a dictator; this dictator seeks, with some justification, to reunite the former empire and rebuilt its strength and sense of national pride. In the 1930s, these trends ran headfirst into an ironclad British and French treaty with Poland. When Hitler tried to take the German city of Danzig back, Britain and France declared war (foolishly, in my opinion), and WWII started, due to the actions of Germany but not due to Germany actually choosing to start WWII.
OK, that said, my answer to the OP's question ...
1 - I don't think anything Russia is doing is any of the U.S.'s business, though we may be painted into a corner at some point by NATO obligations (our equivalent of the British-French treaty with Poland?). We should leave NATO as soon as we legally and morally can do so, in my opinion, for precisely this reason, to avoid getting dragged into a European war.
2 - If war did come, the Russian military is currently no match for the American military. But things can change ... ask the Wehrmacht.
