Yeah, most of those cases are at worst, bad for the next few generations (facing realtively minor ecological damage, rationing and a bad global market) but humanity will recover to some semblance of what it was before. Anything after the late 70's early 80's you start looking at mankind changing almost forever, because that's when you start seeing nuclear weapons going to the aforementioned ahem "Holy Shit" calibre. After that (assuming it's a full blown exchange) you are seeing power shift from the North to the South for a very long time, with nations in South America and the South Pacific becoming major powers due to thier relative isloation (not saying they wouldn't be hit, Australia would probably cop two or three hits but that is pitance compared to what Europe, the US and Asia are going to take). I quite enjoyed reading the timeline Doomsday 1983 which was a TL set after a full blown exchange between the US and the Soviet Union. The two competing powers in the aftermath are the Australian/New Zealand Commonwealth and the South American Federation simply becasue these respective powers escaped relatively unscathed in the exchange.