Texas own official state history book acknowledges some of this, even:
Most of the region's physical and cultural landscape has little in common with the rest of the state. Although it constitutes about 11 percent of the area of Texas, the Trans-Pecos has received less attention than the more populous east.There you go, Texans.
Of course, until Anglo Texians tried to make it so, El Paso never really was part of Texas in the first place. It wasn't part of Spanish Texas, nor was it part of Mexican Texas. We know both of those had the Nueces, not the Rio Grande, as a southern/southwestern boundary. The Llano Estacado, to the west of the headwaters of the Nueces and running north, really was like "unorganized territory," like the land north of Nebraska Territory in the early 1860s before it was officially organized into Dakota Territory.
But El Paso was further west. And on the royal highway between Chihuahua City and Santa Fe. Nobody went east from El Paso 200 years ago, but plenty of people went north and south. In short, El Paso was really either part of today's Mexican province of Chihuahua, part of New Mexico, or part of its own province. El Paso, tis true, didn't have much population, but it was an established city, since 1680, and, as of the Compromise of 1850, more populous than Albuquerque and Santa Fe. (It still is today, but metro Albuquerque is larger than metro El Paso, and the larger Albuquerque-Santa Fe area is larger than El Paso-Las Cruces.)
Today, El Paso is north of the Rio Grande, so it can't be part of Chihuahua. It's about as close to Albuquerque as to Chihuahua City, though, and far closer to it than to Dallas-Fort Worth or Austin. And, given the fact that Texas invaded Mexican New Mexico in 1841, trying to conquer it, shows that early Anglo Texans, despite their claims of the Rio Grande as their border all the way up to its source, really didn't believe that.
So, let's say that as part of the Compromise of 1850, with the feds paying off Texas' massive independence-era debt in exchange for reducing its state boundaries, among other things, those state boundaries, in the Far West, were shoved even further to the east than they actually are.
What would have been some real-world results?
Well, after the Texas oil boom got out to the Permian Basin in the 1920s, New Mexico would be known as even more of an oil state than it is today, because more of the Permian Basin would be in New Mexico. That would have affected the state's broader economy.
Related to that, a New Mexico Territory wouldn't have sold off so many state lands. So, Big Bend and Guadalupe Mountains national parks would be bigger than they are today, and Davis Mountains would be a national park, too. An enlarged southeastern New Mexico, with all of that plus Carlsbad and White Sands, would rank higher as a nature tourism destination.
Politics? If anything, New Mexico would be more liberal yet than it is today. El Paso is as reliability liberal as Austin, and its liberalism is more New Deal worker liberalism than Austin techie neoliberalism. Oh, sure, the rest of the Trans-Pecos would have far-right ranchers and oilmen, but they'd be far outnumbered by greater El Paso.
And, New Mexico probably would have not just one, but two new Congressmen. El Paso's population alone would provide for one. New Mexico's been on the border between three and four representatives long enough that the rural and small-town parts of the Trans-Pecos might be enough to bump it to a fourth representative, not counting El Paso's addition.
Let's say it has five representatives, or seven electoral votes.
Now, let's look at the 2000 presidential election. Bush beat Gore by 271-267. Give New Mexico two more electoral votes and we're tied and headed to the House to decide, not the Supreme Court. (That said, due to the one-state, one-vote principle, Bush likely would have won the House.) Beyond that, a New Mexico with two extra electoral votes makes all of the Four Corners states more important politically in general.
So, thanks, Stephen Douglas and other 1850 Compromise folks, for caving in to Texas pouting or whatever.