People are definitely more divided economically than by race or nationality, especially in this era. Separate ethnicities werea stage in evolution just as separate religions and separate colonies of ants. Greater cooperation overpowers smaller, more independent units. This is evolutionary law. Life changes in favor of greater cooperation, not in favor of greater independence.
Currently there is only one real dichotomy left, the others are fabricated. Economic oppression and control over resources is the only line we need draw in the sand because it's the only source of oppression. All other forms are simply arbitrary, aggrandizing one's own people ahead of others for a false sense of superiority. There are studies showing that this is a purely psychological effect. Meanwhile economic oppression is very real.
Furthermore if races were still divided and fighitng with each other, which ever one had the most mixed origins would come out superior both in intelligence and general disease resistance/fortitude. The Incans were not the most powerful civilization in the Andes from isolation. It was the opposite, they accumulated knowledge by exploring and visiting neighbors and learning from them. Sharing empowers people.