Yet we do the same with the Japanese empire of WW2. And with the Germans and Hitler in WW2. And with South Africa Apartheid. And with that super evil Southern government of the War between the States. The Russians during the Cold war were called by us the evil empire.
Of course it is not true. There is evil in all governments. But when that government becomes your enemy, they are the evil ones.
Good-Ole-Rebel
Yes, I would say that you're correct about how the US viewed the Japanese during WW2. I mentioned in a previous post a sign that quoted Admiral Halsey and was pretty disdainful of the Japanese. I would point out that I had an uncle who was a decorated Marine who fought against the Japanese in the Pacific, but after the war, he developed a very keen interest in Japanese art and culture. He made several trips to Japan and often frequented the Japanese-American Friendship Center when he lived in California. So, even if he ever dehumanized them (and I'm not sure he did), he most certainly "re-humanized" them after the war.
Not sure if Americans saw Germans the same way. My dad told me that some German POWs worked on our aunt's farm in Indiana. I guess they were okay. My dad said that she was told not to give them anything to eat, but she did anyway.
We never went to war with South Africa, and it wasn't until the 1980s that we even made a peep about Apartheid.
As for the North and South in the War Between the States, I think there was some mutual antipathy and hatred, but not with everyone. A lot of Union and Confederate generals served with each other and fought side by side before the war, and it was considered a war of brother against brother. It was a bit too complicated to use the term "dehumanize" when talking about the relationship between North and South in American history. Although it could be said that it's related to contemporary politics and how both sides try to dehumanize the other.
And yes, I think the Russians were probably also dehumanized during the Cold War, as were the Chinese, North Koreans, North Vietnamese, Cubans, etc. I guess they saw all Americans as "Yankees," even those from the South.