I think there is a scenario with a Post-Second Civil War US that is really under explored, and deserve its own unique focus tree and events..... When the conflict is two-sided, due to either President Olson compromising with Reed, or President Garner compromising with Long.
In the older versions of KR back when it was possible for President Curtis/Olson to avert the Second Civil War all together, with the US no longer holding the
Idiot Ball and the immediate crisis resolved, by 1941 a few years later, both the AFP and the SPA would simply have slowly faded into obscurity and back into the political fringe, due to the AFP broken as a political force with the death of Long, and SPA not longer being able to even carry a single state in presidential elections due to the US' post-Fair Deal economic recovery.
.... In the current two-sided Second Civil War scenarios, however, either the SPA or the AFP would absolutely be staying on as viable political forces in the foreseeable future. With either the SPA in charge of the 'National Labor Board' under Olson, or the AFP in charge of the 'Un-American Activities Committee' under Garner. If anything, with the other side getting even more radicalized to the point of triggering the Second Civil War on their own, the side that sided with the Federal government will only get more influential in the foreseeable future after the war.
In the case of the SPA cooperating with President Olson and later Quentin Roosevelt, during post-SACW reconstruction, I can see the SPA pressuring the Federal government towards nationalizing all the companies such as Ford which sided with the AUS, and perhaps advocating on a scheme of land redistribution by seizing farmlands in the South from owners that sided with the AUS, and transferring ownership over to farming cooperatives operated by former sharecroppers
(Organized by the SPA, of course. So that they will have a loyal voter base in the South going forward). While in terms of foreign policy, in this scenario, I think that with the SPA working with the Federal government, it should prevent the US from joining WK2 on the side of the Entente, or at least causing massive unrest from nation-wide solidarity strikes organized by a clearly politically bias NLB, while the SPA actively calls for workplace sabotage and draft dodging in order to sabotage the war effort in any scenario in which the US goes to war against a syndicalist country
(And yes, that includes even if the US is the one side getting invaded by a syndicalist country).
While for the case of the AFP cooperating with President Garner... I think the consequences would be even more damaging to American democracy in the long-termed compared to even a victorious MacArthur going down the Cincinnatus path after his coup. For this scenario, Garner would have tried to end the Great Depression by introducing austerity and cutting public spending in all sectors, especially towards the social security... In exchange for giving Huey Long's Share Our Wealth Society tax breaks, in addition to putting Long in charge of the 'Un-American Activities Committee'... The plan with the austerity measures becoming totally moot the moment the Second Civil War broke out with war-time military spending.... But Long and his supporters will still in charge of the UAC after the Second Civil War agains the CSA. I just cannot see a positive future for the US with this level of cronyism on the highest level of the Federal government. Not to mention you just know Long would be welding the UAC to an even worst degree compared to what McCarthy did in OTL, with the AFP taking advantage of the post-SCW environment to use the UAC as their personal inquisition, arresting and blacklisting anyone that he does not like by painting them as CSA supporters, especially any journalist that dares to look into the corruption in Southern politics. Far from neutralizing the AFP, in this scenario, Long, unless he is assassinated, would absolutely be in an even better position to run for the White House again in 1940....
Just my thoughts on an area that deserves to be explored in more detail.