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?
It's even worse than that. They left the cities unbombed so that they could gauge the destructive power of the weapon on a clean slate. They were literally called tests 2 and 3. Monstrous given the fascists were already on the ropes.