So, further digging into the concept of chronological treatment of South wins ACW in fiction reveals that "A More Perfect Union" is not the first attempt to portray CSA as turning into a fascist state, but it certainly shows a significant break with tradition.
From 1900 to 1961, with few notable exceptions, most AH treatment of ACW that results in Southern victory depicts it as bringing about better consequences than in OTL. Most of these works have three common themes: slavery is voluntarily done away with by the winning South, CSA and USA prosper, and CSA and USA eventually reunite.
The first decade of 20th century AH ACW writing are completely escapist. They try to sidestep the war and at the same time bring about all of its positive consequences (as the writers define them). The best and worst example of this is Ernest Crosby's 1903 article in North American Review "If the South Had Been Allowed to Go". In this scenario, the South is simply allowed to secede by the North, frees its slaves and willingly rejoins the Union at a later date.
The theme of bloodless victory is abandoned in the 1920s. ACW take place in most AH treatments of Southern victory, with the South winning and shortening the war. It is interesting to note that bloodshed is not avoided, but minimized. The South wins in 1861, 1862 or 1863. It could be argued that plausibility wise those are the best years to show Southern victory, but given the scenario (South voluntarily outlaws slavery, CSA and USA prosper together, and CSA and USA reunite), plausibility is not much of a factor here. What the writers are trying to do is to avoid bloodshed or minimize it - to erase the trauma of ACW and make it all "better".
The best written example of this phase is Winston Churchill's counter-alternative (recursive alternate) history essay in 1931, "If Lee had not Won the Battle of Gettysburg". Southern victory at Gettysburg results in Robert E. Lee freeing the slaves; UK recognizing CSA; and US, CS and UK joining forces to create a super-union that polices the world (in a positive way).
The final phase of this direction comes with the publication of MacKinlay Kantor's If the South Had Won the Civil War in 1960 essay for "Look" magazine. Kantor, a Pulitzer Prize winning author, has Texas secede from CSA over differences, and Texas, US and CSA peacefully coexist on the same continent. They fight for Entente in WW1, and then on the side of the Allies in WW2, rekindle the bonds of Americanism and eventually reunite under one government.
During this 60-70 year long trend of depicting South winning as having bringing about good things that help US and the whole continent of North America, there were however a couple of examples of AH writing that showed instead negative consequences of Southern victory.
The most famous is Ward Moore's Bring the Jubille. Published in 1955, the story shows how South won Gettysburg, won its independence and plunged USA into a crisis from which it never recovered. USA is a fifth rate power, jealous of its prosperous Southern neighbor, with only the Empire of Germany being a competitor of CSA.
Another notable exception, is an article by Virginius Dabney in American Mercury, "If South Had Won the War" in October of 1936. The article does something surprising, it is the first time any writer tackling the victory of South in 1863 at Gettysburg chooses to address Grant's siege of Vicksburg. Previous writers of South wins at Gettysburg chose to ignore Grant, Dabney does not. Grant does not lose the siege, but Vicksburg siege lasts longer. This, combined with Gettysburg loss, forces North to the negotiating table and CSA wins. CSA is transformed into a fascist state in the '30s. The fiction is a product of its time, with government after government falling to fascism, the author could not help but be affected by the prevailing doom and gloom mood prevading the times. But, the article is notable for being the first published work of AH that depicts South winning ACW as not a positive act with largely good consequences.
1970 is the first time in fiction, however, that the South is transformed into a true police state, with all the modern tools of dictatorship at its disposal. Which is the work that started this thread, "A More Perfect Union".
It starts the nihilistic streak of Southern victory depiction, which show North America and the world going from bad to worse.
It is interesting to note that the South is not a stand in for South African apartheid at this time. That would come a decade later. In the '70s, it seems the modern day CSA becomes the dark funhouse mirror of US. Anything that can wrong, does. Any part of the political process that can become abused, is abused. All harsh measures ever taken by USA over the course of its history in OTL are magnified and done by CSA on a daily basis. Some of the deeds done are abuse of Presidential power, institutional racism, biological warfare, abd military suppression of civil rights.
Were the authors commenting on their own turbulent times? Perhaps. Were they using CSA as a stand-in for their own vision of what US had become? Maybe. But, the writing got progressively darker and it some works apocalyptic.
Nuclear weapons cast a shadow on most works of fiction produced in this decade and are endcapped with David C. Poyer's The Shiloh Project. Written in 1981 it is the last depiction of the South as the dark mirror of American society before a slew of works would turn South as a stand-in for OTL apartheid South Africa. Poyer's novel builds on most of the themes touched on in the 1970s - fascism in CSA, an emasculated dystopian US, and institutional racism and segregation in North America. Technology is at a lower level than in OTL. The novel details how CS tries to acquire a nuclear bomb ("shell" in this TL verbiage) from US ship passing through, and how an officer in charge of the mission experiences doubts about the society he is defending. The world is nasty and mired in violence, and the tone of the '70s reaches an apotheosis in a scene where a black revolutionary in CSA is tortured into revealing what the Underground Railroad knows about about the Project. Rather than reveal the secret, he summons his strength and bites off his tongue. The ending of the book offers bleak hope - the Southern officer sets off the bomb rather than risk US or CS getting their hands on it and dies with it, as the lover of the revolutionary spirits him out of the country.
The next wave of depiction of CSA features, as mentioned above, South African apartheid comparisson. The first work that starts this trend is the weakest in terms of writing and plausibility - "Captain Confederacy", a badly drawn and broadly written comic book which follows a Confederate analog to Captain America fighting for truth, justice and the Confederate way. I am not going to claim this comic was revolutionary, but chronologically speaking it is the first treatment of "present day" CSA as an analog of South Africa.
I am not done yet with working through the 1980s and 1990s treatment of CSA. I thought I sensed a theme in the 1980s depiction of CSA, besides the South African analog - that of an increasingly weakened CSA as compared to the 1970s. Most of the books, articles and essays that were published seemed to have depicted CSA as not being a threat to world peace, but as a shunned, isolated bastion of apartheid. I was going to work from there, but stumbled into a couple of books that had CSA working hand in glove with present day Nazis as twin powers of the world, and I realized that I also completely ignored the increasingly "military fiction" depiction of plausibility of Southern victory that started in the 1980s, so I'll need more time to put it all together.
