Thus provoked, I enter the fray!
I understand the misconception that real Mexican food is found only in Mexico. Where would you find the most authentic French food? Pretty obvious-France. However, history has complicated matters when it comes to Mexican food. It seems likely the Joe Drape of the NY Times forgot about the Treaty of Guadalupe Hidalgo of 1848 and establishment in 1836 of the Republic of Texas. Prior to this, Texas, New Mexico, Arizona, California, Nevada, Utah; as well as parts of Wyoming and Colorado, were part of Mexico. So, Mexican food didn't "cross the border", the border just shifted south. Imagine the northern-half of the United States being invaded by Canadians and all-of-a-sudden, the food prepared there is no longer real American cooking, ludicrous!
Visiting a variety of regions in Mexico, reminded me that there is no monolithic cuisine in Mexico. There is so much beautiful variety. You'll find that the tortillas in Morelia are different than those in Guanajuato; up north you have wheat flour tortillas; and in Guadalajara, forget the tortillas, it's all about the amazing bread. Ceviche in one coastal area like Zihuatanejo is sweet and saucy, while in Nayarit it's a dry, crumbly and tart. How can anyone say that there is one real cuisine? Can a cook in Oaxaca tell the cook in Chihuahua that her beans are not authentic; not Mexican?
Joe Drape's article in the Times is very enjoyable and in the right spirit. He embraces Tex-Mex food as another one of America's great regional cuisines. I choose to see it in a slightly different light. I think that Tex-Mex, New-Mexican, Californian, are just the northernmost regions of historico-culinary Mexico. This region that goes from southern Colorado and Central California, down to Yucatan and Chiapas have traditions and ingredients that are very similar. Through isolation as well as adaptation, these distinct regions developed their own brand of Mexican food. When well prepared, they are all delicious and unique in their own way.
So "don't be hatin'" on the "Mexican" food of the Southwest, try it. Take it in it's historical context, but most importantly, judge the taste on it's own merits. Leave your baggage at the border and enjoy!