Ever hear of the Nation of Islam? Malcolm X, Elijah Muhammad, some boxer guy? They were black nationalists who wanted to create a nation for black people (somewhere in America presumably).

Essentially if you want a nation made up entirely of one colour people, you're a [insert colour here] nationalist.

Also, you can be a nationalist without being supremacist or racist in any way, though they tend to go together since anyone who has supremacist/racist leanings will see nationalism as taking those views to their logical conclusion.

The reason you don't hear much if anything about black nationalism in America is because blacks will never have enough power to enact it, so it's about as big of a threat as gay nationalism or mormon nationalism - i.e., it ain't gonna happen. White nationalism on the other hand has the latent power to make itself realized if enough people got on board.

That's why liberals go ape-shit over white nationalism and not black nationalism. If blacks were the majority in America, liberals would be going ape-shit over black nationalism and not worry about white nationalism. It's a question of which type of nationalism poses the most tangible risk of coming true, and that depends on who holds the power.