The atomic bombs launched on Hiroshima and Nagasaki are just those unfortunate incidents that, no matter how immoral and devastating they can be, will eventually happen during war conflicts. There's all kinds of atrocities happening against civilians, enemy soldiers and even your own. Japanese comfort women is an example, but pretty much every army, specially Germans and Russians raped people during WWII - International Law doesn't matter during conflicts, it's just words on paper, it's an unfortunate reality. I think America could apologize for the bombs, but then every country would have to apologize for every horrible act ever committed. I can't imagine Portuguese ministers apologizing for enslaving millions of Africans, and it's something I, as a Portuguese, would not do because there is nothing to be sorry about - Those were just circumstances of the time.
Whoever fights monsters should see to it that in the process he does not become a monster. And if you gaze long enough into an abyss, the abyss will gaze back into you