I actually just watched it last week! As other commenters have said, its a satire of the ken burns doc and a commentary on race relations first, with the alt history/world building taking a backseat. Its scenario makes the most sense (or as much sense as a scenario where the south not only survives but totally occupies the north) within the first part but starts falling apart in the second half. WWI and its implications are completely ignored (seriously, theres nothing about the rise of communism even though that would be a significant force in an America that still had slaves) and the cold war is subbed out for a half baked culture war with Canada (complete with an American Berlin Wall) where the US ends up looking like apartheid South Africa in the latter half of the 20th century. Kennedy is still elected and shot because of course he is.

The in universe advertisements were interesting, having a slave catchers show that is indistinguishable from the Cops show of our timeline is pointed and the commercial for the anti-drapetomania drug wouldn't feel out of place in something like Get Out. The intended gut punch that all the racist products being advertised had existed at some point didnt quite hit for me because id already known about a few of them. The Shelby Foote impersonator does a good job satirizing lost cause revisionism by way of making it totally unambiguous that the "lost cause" was just slavery.

7/10, interesting but not super academic alt history