Very true - but there is a Mexican community in East Grand Forks. It's much larger than you think. I think (this is my opinion) the reason why they won't open up an authentic Mexican restaurant is people's tastes in food here don't favor Mexican cuisine, unless it's North Dakotanized...so they'd end up not doing well. I suspect this is why Paulo's slowly changed their food to become more like Paradiso's, but then again they went out of business for other serious reasons.
I'm not sure how it is in Texas, but even in California we still have a mix of "Tex-Mex" with authentic Mexican food. You will see the typical chain restaurants (El Torito, On The Border, Rubio's, Chevy's) that have a lot of Tex-Mex varieties like fajitas and tacos that are fried (traditionally they are not fried). Most family owned "hole in the wall" places are more traditional and stay away from the Tex-Mex. Nothing wrong with Tex-Mex - it's good too (fajitas = yum!).
Where my mother's family is from in northern Mexico (Chihuahua and Zacatecas) they have some dishes that no one in the US usually hears of. Those are a bit more rare in the chain Mexican restaurants but you can find my favorite childhood dishes such as those in north and central Mexico like menudo (cow tripe and hominy soup), nopales (cactus...great with huevos revueltos), fideo, and pozole in the family owned traditional places.
