Genocide is the deliberate killing of a large number of people from a particular nation or ethnic group with the aim of destroying that nation or group.

What the Nazis did to the Jews was genocide. What the Chinese are currently doing to the Uyghurs is genocide. The Circassian genocide in Russia was happening around the same time as the US genocide of the Native Americans.

The troll doesn't understand the meaning of genocide, and doesn't understand strategic bombing. The US didn't want to extinguish the Japanese, and neither the Japanese of that era or the current era believe(d) it was genocide. They had great respect for US General Douglas MacArthur, so much so that Japanese Emperor Hirohito stood side by side with him and publicly declared his respect for his one-time opponent.

Trolls seem to think US schools don't teach this stuff. My children learned it and taught it to my immigrant ass.