Why does race remain such an important factor in the social, political and economic patterns of the united states?

Race remain such an important factor in the social, political and economic patterns of the United States because of the personal opinions and the upbringing of the citizens. Some would always look at the races of the people and would judge them based on their races. Socially, some citizens would not interact with other races maybe because of their experiences or personal ideologies. With regards to politics, they don’t usually rely their government to other races. And with the economic aspect, they view themselves as people with a good economy so why should they go to other races. Though, mostly it would still depend to the citizen's personal beliefs. 

The answer would be political systems .