Why is there a black man in every movie in America?

First of all, American society is inherently mixed. Second, before the American civil rights movement in the 1960s, there were no hard and fast rules on the proportion of blacks in various occupations. However, with the development of sports, the United States has issued many relevant regulations, requiring a certain ethnic group in a certain occupation to reach a certain proportion. In fact, there are not many black actors in the era of black-and-white movies, and there are not necessarily black people in every movie.