It is exactly the opposite. American suburbs were created by goverment policies (specifically, by certain tax breaks for development industry and by tax breaks for home owners, not to mention housing subsidies)
Racism, or more broadly classism -- the refusal to come together in community and the tendency to draw bright lines between self and other, and order society so as to only have to deal with people like self while avoiding other -- is at the very heart of American social structure, at all levels.