There is a mockumentary released some time ago with a similar premise - C.S.A. The Confederate States of America. CSA is frightening in how close it is to true history. The Confederacy came awfully close to winning. The "documentary" is filled with racist ads based on real ads (some are even lifted without alteration). What is even more frightening is how closely it parallels our own society today.
https://www.imdb.com/title/tt0389828/?ref_=nv_sr_srsg_0
To counter the gloom of C.S.A. is Terry Bisson's novel - Fire on the Mountain (PM Press). Bisson has an equally likely, but more hopeful, premise - that John Brown succeeded in starting an insurrection in the slave states.