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?
The Soviet invasion of Manchuria destroyed their logistics chain, caused a majority of their force in the North to rout, and basically made field operations in China impossible. They'd have lasted 3 months tops with 1.5 million Soviet Guards pressing from the north.