Rush Limbaugh says what they are all thinking:

[Hortensis]

12. Unfortunately, we still couldn't let the south go. This time,

decline into underdeveloped nation status would be guaranteed, thanks both to the inherent incompetence and corruption of far-right governments and to climate change. Even the quickest glance at what's happening in many other nations shows it'd end up run by kleptocrats and other organized crime, and impoverished migrants would be desperately trying to flee to safety in the U.S.

Another possibility would be the rise of a militant leader and repeated invasions of the U.S., and even war with a goal of conquest or destruction, driven by fresh water disputes and other necessities, but also the kind of hate and aggression that fueled secession in the first place.

All in all, by far the best option is to place a peaceful but firm electoral stop to their very real threat and otherwise leave them to their birthright of pursuit of happiness without hurting others.