What I'm saying is that there are places where the immigrant Mexican population is so large that they can find success catering solely to that market. Nowhere in Idaho is that true. Hell, even friends from Phoenix who have moved to Denver complain that the Mexican food is bad.
California, Texas, Arizona, New Mexico, and Chicago are all places I've been to with good Mexican food. Seattle, Minneapolis, Spokane, Baltimore are all places I've been to which don't have good Mexican food despite having Mexican restaurants owned and operated by Mexican immigrants.
To put it bluntly; most areas of the country have bad Mexican food, even if the restaurants are owned and operated by Mexican immigrants. Why? because in most areas those Mexican owned and operated restaurants have to cater to their non-largely Mexican immigrant population.