Actually, J.K. Rowling has stated that the names are pretty much meant to be stereotypical. Harry Potter is a stereotypical name for an Englishmen, while Seamus Finnegan is a stereotypical name for an Irishmen. It's an indirect way of clarifying nationalities--with a name like Cho Chang, you can pretty much assume that that person has Asian blood. It's racist because it IS supposed to be racist. xDD So I suppose if there was an black America at Hogwarts, his name WOULD be Tyrone Jackson.