The other thing that gets glossed over in the "it was the soviets, not the bomb that caused the surrender" is that the USSR knew the US had the atomic bomb and

The other thing that gets glossed over in the "it was the soviets, not the bomb that caused the surrender" is that the USSR knew the US had the atomic bomb and realized it might end the war. They had territorial objectives of their own and wanted to join the conflict with (understandably) minimal casualties. If they had thought the war was going to last another year they might waited a bit longer to join. I really strongly recommend Ian Toll's histories of the Pacific war, because there is information that is not in the early histories (at least the ones I read a while back) that is because things in the US and former USSR are more declassified. In particular, the US had a pretty good understanding of what is going on in the Japanese government. They knew a lot of civilian leaders wanted to surrender before Hiroshima, but were afraid they would be associated by a coup, as had happened in the 1930s. That's also what the Japanese leaders who wanted to surrender were worried about as well.