While there is definitely some debate whether it was the nuke or the Russians being responsible for Japan's unconditional surrender, one has to accept that the A-bomb played a large role in the decision. Prior to the bombing of Hiroshima, did the US leadership expect it to be the game changer that it was? Or was it viewed as just another powerful technological edge like the B-29s that dropped it?
No and military leadership was still considering targets for atomic bombings as far as November. General Hull and Colonel Seaman discussed how many more bombs could be built, how quickly, and how to use them on August 13, 1945. This was after Hiroshima and Nagasaki. However, Hull seemed to think that the two bombs did have a "tremendous effect as far as capitulation [was] concerned." In Hull's mind, Nagasaki made a Japanese surrender likely, but not at all certain. If the Japanese did not surrender after Nagasaki, it meant that nuclear weapons could not force a surrender. Hull and Seaman were discussing what to do with nuclear weapons if they had no use in forcing a surrender, most likely neutralizing military forces and infrastructure.
General Bissell felt that, even if the Japanese were to surrender, they would try to draw out negotiations which would be counterproductive to Allied interests. The memorandum doesn't say which outcome Bissell felt was most likely. However, he discusses his predictions for a Japanese protracted negotiation or outright rejection of unconditional surrender.