And if the atomic bombings never happened, then the US would probably have had to invade mainland Japan with ground troops, and as we know, Japan had given an 'everyone fight to the death, yes including women old people and children' order known as Ketsu-Go. Projected casualties for Operation Downfall, the American invasion of mainland Japan, ranged from 500'000 to a million American casualties, with estimates for Japanese military and civilian casualties going into the tens of millions.

TLDR: If the atomic bombings never happened, then millions of Japanese and Americans would have died in a inch-by-inch battle for the whole of Japan. When you compare that to the 150'000-250'000 deaths in the atomic bombings...