Nacodoches definitely has more in common with 'Bama, but El Paso? Not so sure. Brownsville and Matamoros are basically sister cities separated by the Rio Grande, much as Juarez relative to El Paso. In fact, things like the drug war AS war spilling over into El Paso and the Matamoros cult murders of Americans lured from Brownsville twenty years or so ago sometimes make it feel TOO close to Mexico (there's a short list of US Marshalls slain in the line of duty, but one was found in Mexico last year, and it's doubtful he went there since it was out of his jurisdiction. )

Obviously border towns accentuate the similarities with Mexico, just as comparison to Flint accentuates the differences. MI lies well within the part of the US colonized by France, hence they have Sault Ste. Marie and Texas has Corpus Christi. But if you want to see just how strong the Hispanic element is in the Southwest google "Raza Unida. " Mexico isn't the 51st state, but I wouldn't really put it with Central America either, because it's too strongly linked to the US (hence its inclusion in the North American Free Trade Agreement. ) Again, just my impression from here.