I have no problem envisioning an economic downturn in the US, where the national guard becomes a permanent police force against locals so desperate for basic necessities turn to raiding storefronts and waylaying trucks.

This wouldn't be a New Confederacy so much as it would be a thousand little insurrections from coast to coast. But the consequences - loose networks of starving citizens organizing night time raids against warehouses, tit-for-tat retaliatory violence between local police and anti-police organizers, bomb throwers both literal and figurative, and all the military retaliation that would provoke - would look a hell of a lot like a Civil War for anyone living through it.