Think. If there was an invasion of Japan, you might not be here. Your dad, or grandfather likely was going to be sent there and might have been one of the MILLION casualties. Look how they fought to the last man for Iwo Jima. They would fight much harder for the main islands. They were training men, women, and children how to repel us with pitchforks if need be.
Hiroshima didn't make them surrender instantly, how would a demo in the ocean or a remote location do that?
Even after Nagasaki, there was a coup attempt by the people that wanted to keep fighting.