One thing Putin wouldn't expect.

If he's serious about nuking anyone who interferes with his oh, so grandiose designs for Ukraine, tell him to bring it. A counteroffensive on the ground would just be a slow burn towards the apocalypse anyway. The white house should just say "hey, nuke us or fuck off". It'd completely throw him for a loop. If he goes through with it, we were already headed there anyway. If he backs down, hey, we avoided the worst case scenario, so...Cool.