Any armed conflict directly with Russia would be kicked off in the same shameful shambolic fashion we've gotten underway in the last three nations we've invaded. That is to say, we'd make some stupid claims about hacking, everyone else at the UN would chuckle nervously while voting against us, and then we'd ineffectively bomb the wrong targets. Then the world would witness what a bunch of hungry tough bastards with the right equipment can do. It would not be pretty. Eventually Putin and the oligarchs would figure out a really big number we could probably pay if we stopped all entitlement spending for a few generations, and the pain would stop.
Not even Canada would join us in such folly. Putin doesn't actually want a shooting war with USA; he just wants to keep his subjects thinking about Uncle Sam. Let's not fuck up our lives forever, just so a bunch of Washington assholes don't have to admit they've been very wrong for a very long time.