The US military won’t get bored and go home inside the US the way they do elsewhere.

No, they won't. But they also have unique vulnerabilities on the home front that they didn't face in Afghanistan.

• All domestic supply lines now run through potentially hostile territory. Deliveries of food, fuel, and other supplies could become difficult, vulnerable to ambush and attack. Water, natural gas, and electrical lines servicing bases may also be attacked and disabled. Supplies sourced from civilian contracts may also end up being sabotaged by insurgents working for those civilian companies.

• Most domestic US bases are not well fortified. They're generally surrounded only by a fence. A sturdy fence designed to prevent climbing and withstand being hit by a truck, but not bulletproof. And a lot of bases have a lot of important assets within rifle range of the fence. Hit-and-run pot shots taken from outside the fence at expensive and important assets inside the fence are going to become a real problem. Eventually, they'd protect important things with more bulletproof barriers, but that would take significant time, and the troops doing that work would be vulnerable in the meantime. Until those barriers go up, things like aircraft, fuel tanks, and radar systems are going to sporadically end up with random bullet holes in them.

• A lot of federal facilities that aren't military bases are barely protected at all. From courthouses to IRS offices to military recruitment offices, they have a lot of facilities that would be very vulnerable to attack, with a few lightly armed guards at most. For each of those, they'll have to choose between abandoning it or spending significant time and resources in fortifying it.

• A large portion of US servicemembers live off-base, where they would be vulnerable to attack at home or while commuting to the base. Some bases could temporarily house all their troops on-base, but that's probably going to mean putting them most of them up in tents and other temporary housing. Bad for morale. Even worse for morale is that there certainly isn't going to be space for all their families and pets and possessions, which will still be vulnerable to attack off base.

• Defection and desertion will be much larger issues than they ever were in Afghanistan. Pretty much no US soldiers are going to find the idea of leaving the US to join the Taliban to be appealing. But many US soldiers will have mixed feelings about fighting their own countrymen and neighbors, and many may be more sympathetic to the insurgents than to their own command. Some individuals and even some entire units might defect to the other side. Many more will go AWOL and just refuse to fight ... especially if they feel like they need to stay home to protect their own families.

• Spies and saboteurs will also be much larger issues than in Afghanistan. Some of those same soldiers considering defection or desertion might instead choose to stay in their position and aid the insurgency there. A single spy can cause massive damage if he notifies insurgents of troop movements and vulnerabilities. A single saboteur in, say, aircraft avionics maintenance could cause massive damage and bring down several aircraft before being caught. And they will likely find many spies and saboteurs among their ranks in a domestic civil war. Since these spies have the same exact same language and culture, they'll be practically impossible to detect until it's too late. The problem will only become worse if recruitment continues through the war, as it will be almost impossible to avoid recruiting and enlisting new insurgents into their ranks. If they instead pause recruitment during the war, then they're capping their manpower and every soldier lost is irreplaceable.

• As the war drags on, troop morale will become a huge issue (which will feed into worsening the previous two issues). In our previous wars in the Middle East, soldiers would deploy for a limited time, then return to safety in the US (or other overseas bases) where they could rest and train. Usually 6 months deployed, 6 months at home, though deployments could sometimes be longer. In a domestic insurgency, though, none of this could happen. There's no safe home base to return to. It's basically like a permanent deployment, with no end in sight. Being confined to base for their own safety, perhaps having supply shortages due to convoys being attacked, etc will all make troop morale even worse. It will also make recruitment much more difficult.

I think all of that is more than enough to make up for the 'won't get bored and go home' factor.