I don’t know the number of bombs but MacArthur wanted to drop nukes on the Chinese when they joined the fight on the side of the NORKs. The public fight over this proposal led to Truman firing MacArthur.
“I wonder if Japan, without he nukes, would have been another Vietnam.”
A conventional invasion of Japan would have been far, far worse. Vietnam was 50,000 casualties. Estimates for Operation Olympic ran from 1 to 4 million .
In that conflict in 1979, neither side went to all-out-war and the only thing that can be said is that the Chinese failed to get Vietnam to pull their troops from Cambodia. In an all-out-war, either in 1979 or now, the Chinese have to have the advantage, just by size alone. (And the Chinese have no Jane Fondas, then or now.)
But you have to hand it to the Vietnamese commies. They weathered the French, the US, and the Chinese... though with Soviet assistance in the last two and with a major failure of will here in the US, not to mention a lot of high treason on the part of many Americans. Still, the Vietnamese commies did hang tough through all of that.