Russia cant feed a half billion people, and if he is to conquer western Europe by force, hell be Tsar of a wasteland by the time he makes it to the coast of La Rochelle, Bristol and Lisbon. Besides, France and England have their own nukes.
Hell try to interfere in their elections like he does with ours, but I dont see a land invasion.
That said, be REALLY sure you know what youre getting into if you move here. The slow bureaucracy and the paperwork are crushing, and just dont even contemplate it if you dont speak the language of where youre going. Consider how easy life would be in Dallas, Boston or Chicago if the ONLY language you know is French or German. Bring $5 million with you, and sure, the USA will be quick to grant you a green card, but whats your quality of life if you cant communicate with anyone?
It can be done, but theres more involved than packing up and buying a one way ticket. And do NOT give up your US nationality. If things DO get hairy here, the USA cant deny you entry if ever you want to come back, even for visits.