I amn't that well versed in history but if we could somehow check all branches after V-J Day nuclear weapons being used in anger by one or both sides in 1/4 of them would not surprise me. Do keep in mind that it was the 80s before nuclear war would be civilisation ending. Europe and the Soviet Union were toast given nuclear war from '50 maybe, North America had to wait for ICBMs to be screwed given nuclear war and I can't remember if it was Brazil or Australia that were the last places to be targetted by civilisation ending numbers of bombs.

Quantam species suicide I doubt. By the time we could end civilisation the Soviet union was a gerontocracy, albeit one that truly thought the US was an existential enemy when it was barely an enemy. but hey, Stanislav Petrov. I don't know.