In 1945 only 17 B-29s had completed the *Silver Plate* modification program that enabled them to carry/arm/drop the atomic weapons; even as late as as the close of 1948 the Air Force had modified only 60 of the fleet of some 4000 B29s built to carry the atomic bomb.
Neither was there any overabundance of atomic weapons for immediate use; by the end of the war there were probably six devices in various stages of completion usable for support of an eventual invasion of Japan, and when the USAF was established as a seperate armed service in 1947 there were still only 13 in the entire arsenal; 56 in 1948; 298 not until mid-1950.
The idea of atomic weaponry reducing enemy strongholds prior to beachhead landings may have been a happy story intended to boost troop morale, but it's almost certain that the third U.S. atomic weapon would have been delivered to Tokyo... offering the possibility that there would have been no surviving national authority that could order a surrender.
Though the idea of a demonstration strike atop Mt. Fuji certainly offers a certain charm.... Whoops! There go all the cherry blossoms!
But never forget if it wasn't for Germany bombing Pearl Harbor, we wouldn't have gotten involved in WWII.
Well, there was a lot of resistance to Operations Olympic and Coronet following the experiences of Okinawa and kamikazes. IIRC, Adm. Nimitz withdrew his support of an invasion.