OK. How many wars have we fought since that one side surrendered because their empire was lost? We even went to war, indirectly,cold etc with other countries that had nuclear weapons and we only used conventional weapons. We never used nukes and that was even before the other side had enough to enact M.A.D. Ever since WW2, nuclear weapons have been the explanation point and when one side deploys them, it is game over.
The Japanese did find a way to avoid Chinese retribution. They surrendered to the biggest guy on the block and asked for protection, and we have been giving it to them still. Why were we the biggest guys on the block? Only the U.S. had nuclear weapons.