If there is nukes war, it will basically wipe out USA and likely UK as well. Russia probably has significant losses as well but due to its size and terrain plus population density, Russia will eke out a winning population to continue Russia as a nationhood after the war. US will be just left as a oral tradition. I don't think other countries will be affected much other than loss in trading opportunities in dollar. Russia has significantly more nukes than all western countries combined. And that is official numbers. They have their own uranium mines and even US has to import from them. So the number of nukes will be significantly more in the unofficial numbers. Plus, they have access to China as production centres for all the widget they needed. While US by their own suspicion paranoid manner wouldnt engage China for such production needs. With US and UK gone, whatever left as NATO will ceased to exist as they have very little nukes left to counter the remaining nuke countries.