Laos and Cambodia weren't participants in the war but that doesn't really feel like it matters all that much. Whenever I talk about the bombings of Cambodia and Laos with Americans (who - liberals and conservatives alike feel they must always defend) I sometimes here "well we bombed cities in Germany and Japan in WW2 and no one talks about those being war crimes". But were they? I really don't know much about those bombings. My gut says yes they were also war crimes but we just accept them because they were combatant countries?
Yeah this is absolutely not it.
1.) Killing group A because group B is killing group C doesn't make any sense.
2.) That's not what happened, Hiroshima and Nagasaki had no real military significance and didn't change the course of the war in any meaningful way
3.) Collective punishment is morally wrong. Killing a bunch of civilians because a soldier from the same country killed a bunch of civilians is just, you know... Nazi shit. Like literally how the Nazis (and Americans, and French, and British, and many others) behaved when they were attacked by Partisans. Bad look, don't do it.
4.) The fate and wellbeing of Chinese civilians was never considered by the US at any time so far as I am aware.
5.) Japan was ready to surrender and everyone who mattered knew it before the bombs were dropped. America wanted to kill as many Japanese as possible because the Americans who mattered hated Japanese people, and because they spent a lot of money on the bombs and wanted to see what they would do, and because they wanted to show the rest of the world that America could now destroy entire cities with a single bomber, and because they wanted to cow the Soviets who were invading Manchuria at the same time, and for a few other reasons.