The idea that the atomic bombs directly caused the surrender of Japan is contested, actually. It's more likely that they created an urgency in what was already looking like a losing battle. The difference in that situation is that Japan wasn't fighting a war of resistance at any cost against the US, they were fighting as part of an alliance on one front of a world war. In that case it is very real that troops lose morale, civilian casualties become too great, and loss of military assets make victory look unlikely, and then surrender looks attractive by comparison. But I think in the case of popularly supported resistance to colonizers, that threshold is quite high - people feel quite strongly about revenge and are convinced of the justice of their cause in that situation, so the brutality of their colonizers isn't likely to do anything other than strengthen their resolve.

Frankly, I actually think the atomic bombing and firebombing campaigns would be considered war crimes if they happened today. It's really weird that people justify it so much by how horrible the Japanese state was at the time - tons of innocent civilians, including lots of children, died horribly, and it was 100% anticipated, and in the case of the atomic bombing, they did it twice, knowing that. You can't justify your own actions by the crimes of your enemy.