Yes...the new show will be about the South, the democrat party controlled south, winning the Civil War, and keeping blacks as slaves...
....of course, they will find a way to blame republicans.....
'Game of Thrones' Creators' Next Project Explores Alternate America Where Slavery Never Ended
Two main problems, one historical, one in the OP.
The historical --- it would have been impossible for Slavery to have continued. Most of the western world and the Americas had already abolished it before the Civil War started. It would not have been tolerated by that western world, much less the Union. So the premise itself is wildly unrealistic and requires massive suspension of realities.
And two, the "democrat party" (which does not exist) didn't control the South until after, and as a direct result of, that war. Matter of fact the closest match, the Democrat
ic Party, came in fourth in the Presidential election of 1860, its candidate pulling the same number of electoral votes from the South as Lincoln got --- zero. And Lincoln's name wasn't even on a ballot as the Republican Party did not yet exist there.
Moreover Democrats in the North, including Douglas the candidate who came in fourth, worked for the preservation of the Union and against the Confederacy. Lincoln even took one of them on as a running mate in 1864 (and he was a Southerner), forming a new political party "brand" for that purpose.
And more moreover, even your link mentions nothing about political parties. You just plugged that in because you're a moron completely ignorant of your own history.