The Dakotas

Alright lemme tell you about The Dakotas.
During World War 3, some jerkface terrorists ruined Lake Erie with toxic sludge. Yeah, I know. Who does that? Well it turns out it was members of a growing political party in the United States called the Northern Rangers for Liberty (NRL). How do we know this? The government told us so.
So we tried to round up all the U.S. citizens who were a part of this group.  A lot of them came from North and South Dakota.
Apparently invading the Dakotas was hard to do, because the Northern Rangers were really prepared for some guerilla warfare shit. And honestly, it seemed like the government was right, because it also seemed pretty obvious that the NRL were being supplied weapons from an outside source. Someone was trying to sow discord in the good ol' U. S. of A. and it was working.
So instead of rounding everybody up, we just locked them in. We secured the borders of North and South Dakotas and with only a modicum of help from those smug Canadians, but I won't get into that shit show.
Now The Dakotas have been walled off from the rest of us, and the citizens there are in the largest internment camp in history. Sometimes they try to go through reintegration processing and get back on the good side. But that process is hell, even when you do get back into society they watch you like a hawk.
Alright, that's the idea in a nutshell.

IT'S ALL BADLANDS NOW

There's over a million people in The Dakotas and they're getting little support from the government. Once the walls went up, the rats turned on each other, and the Northern Rangers for Liberty splintered into different factions. The most powerful ones control the water sources, like the Missouri River.
Don't get me wrong, there were probably some confused people in the NRL who just got caught up before things got out of hand. I get it. But those people are stuck out there fending for their lives, because if you ain't with the NRL, you ain't with anybody.
Every once in a while we send in some crazy green berets who want to walk on the wild side. They go in there and stir the pot, just to keep them going at each other other's throats.

NATIVE AMERICANS

So you're probably asking yourself, what about all those reservations for the Native Americans? Did we go in and fish them out and place them somewhere else in the country? Not really. I mean, some of them left, but seeing as how our country had treated them pretty unfairly, to say the least, they figured they'd rather take their chances in the Badlands.
The government understood and only asked the remaining tribes that they stay out of the mess between us and the NRL. I don't think they even gave a shit to reply to that one.

ILLEGAL REENTRY

Sometimes folks sneak back into the country. Maybe there's a border guard who takes a bribe or has a soft heart. But more often than not it's because they sneak into Canada and back into the country along through Montana or Minnesota.
Canada thinks this shit is hilarious. I think it's a disgrace. But whatever.
Some of these folks reentering the country are real bad hombres wanting to cause a little havoc in our country, like they did with Lake Erie. But a lot of the times they're just regular people looking for a way out of that hellhole. Those sad few are most likely rounded up by even worse people than the NRL, I'm sad to say. Lots of folks from the Dakotas end up as cheap black market labor. It's a sad world, I tell ya. There's bad folks everywhere.

THE OIL FIELDS

North Dakota was the second highest producer of oil in the United States. You can't just give that up. Places like the Bakken Oil Fields became warzones, with pipelines being destroyed. Securing the oil fields became a high priority, so you'll see the most military presence there.
It seems like every time they get the rigs going again, there's another bombing. I'm no math-magician, but I figure at some point it's not going to be worth fixing up.

HUMANITARIAN AID

After a while, folks started to say the treatment of The Dakotas was inhumane. You know, like when they turned Lake Erie into toxic tea. A bunch of bleeding hearts decided that we needed to send folks in there to give them medical attention or food.
One doctor, named Dr. Eileen Sparrow wrote a book about all the stuff she saw. Folks got really fired up then, looking to reeintigrate Dakota citizens back into the United States or improve their living conditions. I haven't read the book, but it sounds like baloney to me.
As far as I'm concerned, the Northern Rangers for Liberty hated technology and wanted to live a green life off the land. Well have at it boys. I'll be over here with my American Flag and air conditioning.