On August 10th, 1945 the U.S. had exactly as many atomic bombs as any other country in the world. The U.S. had the capacity of producing approximately one nuclear weapon per month and fully intended using them Target number three was Tokyo.
The U.S. actually drew up schedules and was making target lists. Ironically, Hiroshima had been largely spared conventional bombing because the U.S. wanted to keep it pristine to evaluate the effect of atomic bombs. The locals believed they had been spared because many people from the Hiroshima area had emigrated to the United States during the late 19th and early 20th Centuries.
The USA had several Thin Mans and considered converting every one Thin Man into 8 Fat Mans. Was that true, still classified or false? I know a lot about the nuclear weapon programs, but I don't know that.