The Desert is a pretty vast region of Medieval America. And to eyes in both the present and the future, it may be the most outright alien. Encompassing much of the southwest, these nations have probably been kept isolated from the rest of the continent by plains and mountains. And kept isolated from each other by desert. The most distinct thing about each of them, from what we can tell so far, is that they have wildly different religions. Religion seems to be the best way to divide the three nations, if not states up. When White mentions peoples west of the Rockies, he seems to emphasize the religion. It makes sense as in the East, Warlords and Churchmen are distinct entities, but here there's no such separation of Church and Military. As a result, I think the soldiers there may have religious as well as secular duties. Some places, like Colorado and Nevada look to have three religions within their former borders, but that might not be a case of friction so much as petering out. In fact, Nevada itself seems to withered away, with no tourism industry, or technology to divert the rivers. The settlements of the desert may have suffered the most traumatic transition into this era, as the southwest is home to many bustling and growing cities, with the relative lack of resources to support it. It's said these places might never have attracted people in the first place if air conditioning wasn't invented. The climb back to the top must have been harsh, maybe even gruesome at times, but distinct nation-states were formed.
The lifestyle icon is a water pump denoting "irrigation". White has dropped reference to the fact farmers need to irrigate their land, building canals from rivers to farms in order to grow crops. The sunlight and lack of parasites make up for the shallow soils, but agriculture remains intensive. Civilizations pretty much appear on the river banks and nations are long, narrow bends and arcs. It's likely that not only do the rivers serve as the bases for farming, but also transport and fleets. This is another reason hydraulic empires are able to thrive with absolute authority. Cities are very condensed and built on a single route. White doesn't have any pictures, even in the archive, of what people in the desert look like. However, we probably don't need to imagine it too much. I think during the day, the farmers dress like the Southeast farmers, except maybe implimenting designs of the local culture. Something resembling the Middle Easter kaffa may be worn to protect the neck. Alternate sets of warmer clothes may be kept, as the desert gets very cold at night. However, half the desert population isn't made of farmers, but of herdsmen. They may look a little like their Plains counterparts, except maybe a little more colorful. What also makes this desert region distinct from the Middle East and Sahara is the Rocky Mountain range. These very high altitudes probably means desert dwellers are not completely unfamiliar with cold. The shepherds may even dress a lot warmer than desert nomads we're used to. Ice may also be feasible for the wealthy to access, which could affect society in several ways.
Most of the population of Mexico is found in the more forested, south, and the "border towns" of the desert are now firmly nomadic. In my opinion, this means that the territory is relatively up for grabs. Why would a nation want this area? Well, I think they would want the area around the Baja peninsula. Trade with South America probably shapes the mobility and initiative of the north, and the Gulf of California would make an excellent trade route without having to traverse the inland deserts. The main problem is how arid Death Valley is. These would not be great sources of agriculture for the region--they would be trade cities, plain and simple. A breakdown in trade, or a wane in demand for the goods would see such cities wither and die.
First we have New Mexico, which also seems to include Arizona, and even the edge of Texas. The desert shepherds and goatherds may play a very large role in New Mexico. The husbandry map combined with the West Map shows that within New Mexico's borders, we see quite a few nomadic tribes. They may even make up half the population. It's not so surprising since New Mexico and Arizona have always been more "Wild West" than the other desert states, and still boost a few ranches. Most are shepherds and goatherds, but it's possible at least 100,000 or so are cattlers. Another interesting thing is that the major cities seem to mostly be in the eastern half of the nation. However, there are settlements on the Gila river. I wonder if they're more spread out, and most resemble the old Native American cultures which have likely blurred over history. The religion map says "New Age", and I'm not sure what that is, or why primarily Catholic New Mexico would be practicing that. It's possible that, with the sun belt's collapse, people were looking for drastic new answers. The religions of the modern westerns world come mostly from the desert (The same desert, in fact), so it probably makes sense that if anything dramatically different were to pop up, it would be there. And it would probably take just one eccentric emperor to impose his new faith one everybody.
Speaking of which, Deseret is one of the more interesting parts of the country--it seems to be a nation that exists by force of will, with only a few things to keep it together--its place as a trade hub, and its unique religion. It's not unrealistic for a theocracy dominated by Mormons to do reasonably well during dark times. The Church of Latter Day Saints preaches self sufficiency, and many of the members are known to store a great deal of food. Probably the biggest contributors to Hurricane Katrina relief were Mormon organizations. As I've mentioned before, I imagine the army consists of warriors known as "Templars", named after the order seen during the Crusades, and reasonably appropriate considering Salt Lake City's monastic center is called a ""temple". Right now, it's thinking of expanding into less arid regions, and I wonder how that would effect its Hydraulic Empire status.
And finally we have California. Or "The Californias". It seems this is two nations in one. The thing is, there's a fiefdom dominated by the Church of Scientology. But it also holds spiritual authority over the "Republic" of California. So it's hard to imagine just how that structure works. Is it like the Holy Roman Empire? White does mention that every now and then, the San Francisco is conquered by armies from the Pacific Northwest. (Perhaps a reference to the Bay Area not quite between the Northwest, and not quite being Southern California) The California area in general though, seems remarkably wealthy. The husbandry map shows the regions has the most farms west of the plains. And the trade map indicates it may have the finest goods of the west. Where the east is concerned, California may almost be legendary, with its sunshine, various fruits, and maybe even an insane amount of gold. Whether it produces that much as the time is besides the point; It's almost certain that in the east, lore about California has reached a mythic status. Speaking of California and myths, as I mentioned in the religion article, I think much of California's mythology is steeped in American pop culture, particularly Hollywood films. Star Wars may be the quintessential epic, especially since Scientology is a very celestial religion. I would bet Emperors often claim they're made into stars upon death--and local astronomers are bribed to name stars after their recently departed rulers.
Finally, I wouldn't be surprised if the Free Zone is home to the world's most stunning menagerie. Once upon a time, Southern California was home to the San Diego Zoo. Because of the Mediterranean climate, a few megafauna were able to make their home there, and eventually colonies of beasts went undisturbed. However, California is much more rigidly structured, and once Empires started popping up, they quickly collected these beasts. Some for exotic pets of the upper castes, and some for the fabled Labyrinth. The greed and short sightedness of some empires has probably kept megafauna from thriving as much as in Florida.