So let's play this out:
Orrorsh reality in old southwest: Already covered. (BTW, it's not just Los Alamos... there's Roswell, Sandia National Labs, Area 51, Kirtland AFB). One thing I did forget... lots of oil drilling on public land, especially with the Permian Basin and fracking technology. Don't forget the haunted graveyards and restless spirits from the various massacres and tortures from the 16th century Spaniards on.
Pan Pacifica: Maybe not the best fit. There is the Tesla gigafactory, Intel chip fabs, oil resources, and some tech, but generally no the coolest interaction. Maybe the Men In Black type conspiracy stuff. Maybe there really was some alien tech here the PP wants to get ahold of, though if so, why not just steal it through normal means?
Tharkhold: Now this could be a lot of fun, and might be the best combo. Lawless gangs of demon outlows. High tech government trains carrying cargo. Oil pipelines that need protecting from Mad Max bandits. Chop shop surgeons in the saloon and very, very nasty organized crime. Unlikely bands of heroes for hire. Maybe the zone gets corrupted or weakened and is a mixed zone. Corrupted spirits and magically irradiated blasted lands with ancient buried horrors. Apache burial grounds. Hope + Dominance. Glory + Pain.
Nile Empire: Basically, the Weird West. Or the Wild Wild West with Will Smith. https://www.youtube.com/watch?v=wk4QqIeZ9Xk
. I think we all know what it's like, and it's goofy and fun, though maybe too close to the regular Nile Empire.
Cyberpapacy: Not the likeliest target (why here? so far, and what's worth getting?). Also, I don't know if the reality would carry any of the southwestern flair, and the CP would try to crush everything that makes the area interesting from a game play perspective.
Aylse: I like this combo almost as much as Tharkhold, because Aylse Tech is just high enough to have primitive pistols and blunderbusses and airships. But you get something like the lone gunman knight, the spellslinger on horseback, possibly a bit of steampunk technology, dwarven outsiders who are doubly outcast, native american dreamwalkers and medicine men who mix magic and spiritual powers. But, why does Uthorian spend the energy to drop a zone here? Especially with a full bridge and stellae, right in the middle of Kaah's backyard, early in the war?
Here's an interesting idea... Mobius is going to drop a reality bomb in Los Alamos (how cool is that?) - not stellae and doesn't even require a tree. But he's foiled by storm knights, who then lose the bomb to agents of another high lord who convert it to their reality. The bomb gets detonated, but has an unpredictable effect