Why the scare quotes? It is still debated, and the fanaticism of the Japanese resistance (for instance, in Okinawa) makes a fairly compelling case that a land-based invasion of Japan would be extremely costly for both the invaders and the civilian population.
> Or spray them with agent orange?
It's pretty terrible as a weapon of mass destruction. Don't you think that if the US had wanted to annihilate the population of North Vietnam, they would have employed something a bit more direct?
Comparatively, I don't see the general disregard for civilian casualties exhibited by the Saudis in their ongoing bombing campaign in Yemen as a sign that they intend to wipe out the population wholesale.
> Or just help Suharto get rid of some millions and let him do the footwork?
Don't get me wrong, I'm absolutely not condoning the US foreign policy. But I don't see the US involvement in the mass killings conducted by Suharto as something racially motivated against Asians. It was a case of "the only good communist/leftist sympathizer is a dead one".