The U.S. really had no choice but to drop the bomb. Japan was arresting citizens who talked of surrender so even a full scale invasion of Japan would result in at least hundreds of thousands more deaths. The atomic bomb was a surprise and shock (even though we warned Japanese citizens). But the bomb did kill almost 200,000 Japanese and got the attention of Russia so you can kinda argue for both sides. Plus Japan didn’t surrender after the first bomb, so America was forced to drop another.