Would have been hell for the Soviets and Europe but just really bad for the US. Everything I’ve read about a war in the 50’s postulated that maybe a dozen nukes would have hit America. The soviet ICBM force was small until the late 60’s, that’s why Cuba was so important to them. Their bombers would have been the real issue and getting through Canada would have been very hard for them.
A dozen would have been bad enough. Luckily, Communism fell without a major war being waged. While Russia is resurgent, at least they are not Communist. One could almost argue that we are becoming more Communist (Socialist) than they are.
Of course, these days, the Muzzies seem like a bigger threat.