The general presumption on Nuclear Deterrence is that if one party uses their nukes then the other - presumably defending - party will be forced to do the same. Even if you're not going for a MAD scenario. So even if we don't want a strike against Russia, we probably will.

That is of course unless the nation is ran by The Boss. Then we'd probably get glassed with no retaliation so that there can be at least some power left standing to keep stability over the planet.