As much as I hate that it happened and demonize America for doing it, I think without Hiroshima and Nagasaki, we would have had a nuclear exchange by the 1960s. They were begging to have one with stuff like this. MacArthur wanted to nuke the Chinese during the Korean War.
But the results were clear, the absolute horror it would cause, and I think that's the only thing that held the people at the top back.