These communities formed from escaped slaves; that is to say, from people who "suffered" from drapetomania (can you believe antebellum physicians diagnosed this condition after being asked to solve the great mystery of why slaves would try to escape?) Several things about this are striking; for example the understated influence of the Caribbean colonies on southeastern U.S. culture (listen to this Gullah speaker's accent when she's speaking English. She's a native-born South Carolinian!)
The question is why the quilombos seem to be a much more present part of Brazilian history than these communities are a part of American history. Both countries have a history of slavery; there must be something else associated with this difference.