I definitely don't think we should go to war with Russia over Ukraine but I think you're misunderstanding on what we would have to actually do to win a war with Russia over the Ukraine. We would not have to do what Nazi Germany or Napelon's France did, we wouldn't have to invade and conquer Russia. What we would have to do is kick Russia out of Ukraine and keep them out, which has been done. Remember World War I Germany with her allies was able to basically cause the downfall of Russia without having to conquer her, they simply needed to wear her down.
Now to even do this we would most likely need to reinstate the draft and would probably be locked in the most brutal war since Vietnam or even World War II but I do think we have the capabilities to win in the end.