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?
If you want to see this in action in the present day; What America and Saudi are doing in Yemen is an order of magnitude more destructive and murderous than anything that has happened in Ukraine, yet American and European commentators are breathlessly calling for war crimes trials against the Russians.
Because only bad countries do war crimes