Thoughts on a couple of things:
First, NM Mexican food, it really depends on where you’re going of course. Places that cater to locals run the gamut of cheap-filling-no frills that while better than Taco Bell are all about stuffing you fast, to local ingredients cooked with care and pride (sublime), to fine ingredients cooked to the tastes of tourists / upscale gringos and made to look beautiful on a plate (not bad but boring). I lived for 12 years (6-18 in Las Cruces) and 2 years in Albuquerque. The places you went with friends and family were very different from places you took out of town guests! 95% of the places that had mariachis were right out!
I agree in Texas, Mexican food is -highly- variable, but as a rule of thumb, the farther from Kansas/Panhandle beef country, the better it was. I hate El Paso like the plague, but it had good Mexican food. Lubbock and Amarillo though, -shudder- no, just no. Galveston, Houston, Corpus Christi all had solid Mexican food, although again, had to head away from the main tourist drags for the best stuff.
As for Austin, I do love a lot of the food there, but will agree that Torchy’s is absolutely fine, but not authentic, for whatever value you want to use for that term. It’s much more about selling interesting combos with funny names, and as they’ve hugely expanded the chain, lost a lot of the “Keep Austin Weird” elements in favor of increased profitability. But it isn’t bad tacos by any means.
Back to regional/specialty food.
My biggest grief is New York (or east coast) style deli. My father spent years in Philadelphia, Massachusetts, and New York, but moved us to Las Cruces right before I turned six for various reasons. He raised me with a love of Jewish / New York style deli that has stuck with me all my life, but there was -one- place in Cruces that did it to within his tolerance, and almost even place in the Southwest is at best a pale imitation of what the great delis of the coast manage. And we won’t even talk about fast food / fast casual delis - they aren’t horrible, if you set your expectations appropriately, but just a nope for me.
Another regional thing from my NM days is green chile cheeseburgers. You have to understand, it’s an assumption there that every place will have this, even McDonalds does so. But outside of NM, it’s less common, and is likely to be defined as throwing pickled jalapenos on a burger, or some sort of chili sauce on a burger. It offends me at almost a cellular level, so I have to make my own, or to make sure to get a fix on my drives to visit family once every year or so.