I don't see how anybody could say that wasn't a mistake.
It was bad, but certainly not the worst decision the US has ever made, and arguably not as bad as bombing Hiroshima and Nagasaki, which did kill around 3000 US nationals.
Dropping the atomic bombs was the right decision, in my mind, because if we hadn't done that, the Japanese probably wouldn't have surrendered as soon, and the war in the Pacific would have gone on indefinitely, with potentially many more lives lost than at Hiroshima and Nagasaki. While it wasn't ideal, it was the quickest and simplest way to end the war and minimize future losses for both Japan and the United States.
