He's BLACK, and he's called BLACK Panther

I wouldn’t read too much into it, just Panther or The Panther isn't as cool sounding.

Scarlet Witch, Green Lantern and Red Skull all sound better with a color added to their name just like Black Panther, whereas some like Black Widow and Black Cat have a deeper meaning.

Stan Lee or Jack Kirby probably thought Black Panther sounded cool and left it like that, just like the random color they gave Hulk after his original color of grey was dropped. When you think about it red would of better suited Hulk as red is the color of rage, but they didn’t give it much thought.

He became American when people stopped being able to recognize obvious satire