As others have said, there are lots of divides in various cultures. From what I have heard, many people from the Americas look down on those from further south in the Americas. (Americans look down on Mexicans, who look down on Guatemalans, etc.) I’ve heard there are still certain views regarding Han Chinese versus others in China, xenophobia in Japan, sectarianism between subsets of Islam, and a basic level of nativism throughout much of the world. For America, the culture started with the era of ‘scientific’ racism so it started with a color divide. Those old divides remain because certain classes of people keep reinforcing because it helps their narrative. In the same way you can look at what happened with American healthcare through a Marxist, free-market-absolutist, or various other views, you can look at America through various lenses, and the racial one still holds a lot of sway. As long as enough people identify with the grouping, it grants political power to those who have authority in that group. The power is used to reinforce the identity to perpetuate itself and the cycle continues. It takes fairly drastic circumstances to change that.