They are, they just don't fit in the naming convention that you have in your head. "Confederatism" we talk about as "The Lost Cause", although I'd prefer "Neo-Confederates", and Segregation we just don't put "-ism" on the end, although adherents to it are generally termed "Segregationists". "Slaveryism", thankfully, isn't much of a ideology any more, but you'll here pro-slavery thought be talked about as Herrenvolk Democracy, perhaps, when looking at an American context, although hardly the only term. There is no inherent requirement that we must talk about political ideologies as "-ism", and that is simply the case here. But just because we don't use that naming convention doesn't mean we don't talk about them, and if anything, they are some of the most dominant themes in how we discuss and understand American history.

We have quite a few older posts that talk about these political ideologies and their place within the American political landscape. This post on the Lost Cause is especially useful, but there are plenty more to search for.