Also, "Tex-Mex" is an inaccurate term for most stuff. Qualities that people attribute to Tex-Mex are really Santa Fean.
The excessive cheese thing, for example: Santa Fe was the major trade hub between the French and Spanish for almost two centuries. The French would bring all their cheeses down and put it on everything.
Pico de gallo is another good example. "Real" Mexican Pico is much saucier and less aromatic. The chunkiness and excessive cilantro were also French things.
And there's a lot of other stuff that people call Mexican but isn't really Mexican at all. It's Pueblo.