I do not think you can get around the fact that these bombs were weapons of mass destruction unleashed on civilian populations in order to create horror and terror.
I think historians will debate until the end of time if their use was justified or not, as the aim in their use was to stop the war, and prevent the invasion of the Japanese homeland, which may well have led to many many more deaths (including both American AND Japanese deaths) than the two bombs. And I really do not want to get into that, as this does not seem the place...
But nonetheless, I have no problem with any sort of apology (implied or direct) from the US government for the use of these bombs - especially if directed towards the poor people who managed to somehow survive them.
The Allies did some pretty terrible things in World War II. No death camps or rapes of Nanking, but you have the bombings of civilian areas, the needless destruction of the historical abbey at Monte Casino while it was stuffed with hundreds of refugees, the concentration camps for Japanese-Americans, the atomic bombs, and your usual random war crimes like gang rapes and shootings of random civilians by soldiers. And you know what - it does not matter that the enemy was doing infinitely worse things - they were still atrocities.
(I think the same thing of the far left ones, too, though they seem to get a lot less media attention. We have a far left one on Detroit radio on Sunday nights. He is a fruitcake.)