A retired Black NCO whom my brothers knew and worked with in the 80s commented that when he had race and discipline issues in the military, it was with White Northerners, not White Southerners. Indeed, in civilian life in the South, Black veterans tended to be respected for their service and ability. An older Southern white whom I knew in that era did not like or trust Blacks as a group but was unstinting and sincere in his praise of a retired Black Army Major who had been his boss at IBM.
Divide and conquer. If we're all Americans, the Left would be out of power. They didn't want that.