It's amazing to listen to the words of Obama when comparing them to other Presidents such as Roosevelt, Truman, Kennedy or Regan. Victory isn't something to be sorry about or to apologize for. Victory is something to be proud over. We didn't make a mistake in WWII what we did do was respond to an unprovoked attack, at Pearl Harbor. What we did was save Europe from becoming annexed by Hitler and becoming a new Germany. WE have nothing to apologize for. While the nuclear bombs dropped did kill an enormous number of kids and innocent people it also saved the lives of countless of others.
If not for the Japaneese Emperor the war would have continued and another bomb would have needed to be dropped. There were some in Japan that felt that EVERY life, innocent included, should be given in defense of Japan and the Emperor, whom they considered as God. Dictators such as Hitler care for themselves and care not for anyone else and use their citizens as pawns in order to serve and meet their own selfish needs and desires.
Regarding the bombing of these cities most of those who died did so in a blink of an eye and while yes there was some that suffered greatly most of those killed most likely never knew what happened and it was over in a second. Most also don't think that these weapons would not have been used or necessary if it wasn't for dictators who would eliminate whole groups of people or a whole nation of people and are uncaring about what pain and torment they would unleash upon people.
Far more destructive and horrible were the incendiary bombs which were dropped on other Japaneese cities that killed by fire and heat and sucking oxygen out of the air. At least for most the atomic weapons killed instantly. Today what is sobering is that the weapons we have are so much more powerful and destructive and there are so many more of them. The problem is that war is horrible and a necessary evil at times and when you go to war you don't go to be friendly or compationate but you are compationate by getting it over as fast and as strongly as possible.
You don't prevent wars by being weak but you prevent wars by being the most powerful player to where no one would dare to confront you. Weakness prompts wars. There are always (have been and will be) idiots and insane people that seek domination and care little about others but want total power. You don't dissuade people by being friendly or weak but rather with overwhelming power and dominance. Of course, as with everything, that is my own opinion.