Before the United States dropped the atomic bomb on Hiroshima and Nagasaki, the Japanese government was willing to invest everything into winning, training their troops to sacrifice themselves for the cause (ex. kamikaze). Even young children were being brought up with the goal of fighting. Despite Japan suffering quite massive losses, they were still sending practically every available person to work for the war effort. Therefore, I think that if the United States had not dropped the bomb, Japan would not have surrendered, which is corroborated by a number of documents written beforehand by officials.
