After looking over the prototype map I noticed that there are no Arizona cities to be found.
To more effectively represent this part of the world I would suggest doing the following: remove the city of Chihuahua from the map and use Juarez, Albuquerque, and Phoenix as the US/Mexico border.
Here're some reasons why...
First is population density. The cities in the Southwestern US and Northern Mexico that did make the map are Chihuahua, Ciudad Juárez, Albuquerque, Denver, Salt Lake City, and Las Vegas.
The Phoenix metro area is the largest urban area in the region--larger than all of the other cities in the region that did make the map. Oddly the Mexican state of Chihuahua gets two cities on the map even though the Phoenix metro area has a larger population than that entire state of Chihuahua.
Second, the Nogales/Tucson/Phoenix corridor is a major corridor for cross border traffic. It's the biggest transit node between Texas and the west coast.
Third, and most important, the game is more thematic with Arizona included. The state of Arizona produces more wattage of solar power per capita than any other state in the US, in addition to power from hydro-electric, nuclear, and fossil fuel sources.
Things that are done right...
I don't want to sound negative, and I'm certainly going to buy a copy of this game. In particular there are a number of things that I like about the rendering of this part of the world.
I like the fact that the larger Ciudad Juárez is included instead of the smaller El Paso, especially since there are already three other Texas cities on the map.
Having spent a lot of time in New Mexico--a state with a relatively small population compared to other states in the region--it's nice to see Albuquerque get some love.
Also, the high connection costs between the US/Mexico border and the rest of Mexico are very much appropriate considering the rough terrain, arid climate and low population density of the region.
Including the recommended change would do an even better job of reflecting this part of the world.