The Japanese surrender in World war two was a sudden shift from their previous war plans, So what if the cause for their surrender was not directly caused by the Atomic bomb?
Could we Perhaps assume that the A Bomb was dropped to warn the Russians, not to end the war. the Japanese would have fought to the last man [there was even an attempted coup after the A Bomb dropped by Japanese generals to ensure their continued fight against Allied aggression.]
Perhaps the reason they surrendered to the US was because the Russians were massing on their Western front from Sakhalin and Vladivostok and the Japanese imperialists realised that under Russian rule their way of life and emperor would be no more. this would be why several weeks before the bombs were dropped on Hiroshima and Nagasaki they had sought a way of offering a surrender to the US and its allies that protected their way of life.
The US dropped the bomb because they wished to show the Russians they had developed this weapon and to keep them in line, it had very little effect on the Japanese war machine itself, even going so far as to mobilise the Japanese generals I mentioned earlier to stage a coup to continue the fight to the last man.
It is probably worth reading up on history before accepting the US cry of "we won the war". The Russians won the ground war for the Allies in Europe while the US was sitting on the sidelines increasing its economy by ripping off the other allies through the lend lease agreements until they were forced to enter via the Japanese attack on Pearl Harbour.