What are the uses for omitting that America's first non-native populations were black?

From the text:

American history textbooks cannot be faulted for not mentioning that the first non-Native settlers in the United States were black. Educationally, however, the incident has its uses. It shows that Africans (is it too early to call them African Americans?) rebelled against slavery from the first. It points to the important subject of three-way race relations Indian-African-Europeanwhich most textbooks completely omit. It teaches that slavery cannot readily survive without secure borders. And, symbolically, it illusttates that African Americans, and the attendant subject of black-white race relations, were part of American history from the first European attempts to settle.