Tex-Mex

Tex-Mex cuisine (from the words "Texan" and "Mexican") is an American and Texan cuisine that derives from the culinary creations of the "Tejano" people of Texas. It has spread from border states such as Texas and others in the Southwestern United States to the rest of the country.
Tex-Mex is most popular in Texas and neighboring areas, especially nearby states in both the US and Mexico. It is a subtype of Southwestern cuisine found in the American Southwest.
Common dishes.
Some ingredients are common in Mexican cuisine, but others not often used in Mexico are often added. 
Tex-Mex cuisine is characterized by its heavy use of shredded cheese, meat (particularly beef, pork, and chicken), beans, peppers, and spices, in addition to flour "tortillas". 
Sometimes various Tex-Mex dishes are made without the use of a "tortilla", a common example of this is the "fajita bowl", which is a "fajita" served without a soft "tortilla".
Generally, cheese plays a much bigger role in Tex-Mex food than in mainstream Mexican cuisine, particularly in the popularity of "chile con queso" (often referred to as simply "queso"), which is often eaten with chips (alongside or in place of guacamole and salsa), or may be served over enchiladas, tamales, or burritos.
Moreover, Tex-Mex has imported flavors from other spicy cuisines, such as in its use of cumin, introduced by Spanish immigrants to Texas from the Canary Islands, but used in only a few central Mexican recipes.
History.
During the mission era, Spanish and Mexican cuisines were combined in Texas as in other parts of the northern frontier of New Spain. 
However, the cuisine that would come to be called Tex-Mex originated with "Tejanos" (Texans of Mexican descent) as a mix of native Mexican and Spanish foods when Texas was part of New Spain and later Mexico.
From the South Texas region between San Antonio, the Rio Grande Valley and El Paso, this cuisine has had little variation, and from earliest times has always been influenced by the cooking in the neighboring northern states of Mexico. 
The ranching culture of South Texas and Northern Mexico straddles both sides of the border, where beef, grilled food, and tortillas have been common and popular foods for more than a century. 
A taste for "cabrito" (kid goat), "barbacoa de cabeza" (barbecued beef heads), "carne seca" (dried beef), and other products of cattle culture is also common on both sides of the Rio Grande.
In the 20th century, as goods from the United States became cheap and readily available, Tex-Mex took on such Americanized elements as Cheddar , jack, and pimento cheeses.
In much of Texas, the cooking styles on both sides of the U.S.-Mexico border were the same until a period after the U.S. Civil War. With the railroads, American ingredients and cooking appliances became common on the U.S. side.
A 1968 "Los Angeles Times" feature wrote "[i]f the dish is a combination of Old World cooking, hush-my-mouth Southern cuisine and Tex-Mex, it's from the Texas Hill Country."
Outside the US.
In France, Paris's first Tex-Mex restaurant opened in March 1983. According to restaurateur Claude Benayoun, business had been slow, but after the 1986 release of the film "Betty Blue", which featured characters drinking tequila shots and eating "chili con carne", "everything went crazy." According to Benayoun, ""Betty Blue" was like our "Easy Rider"; it was unbelievably popular in France. And after the movie came out, everybody in Paris wanted a shot of tequila and a bowl of chili."
Tex-Mex has also spread to Argentina, India, Japan, Mexico, the Netherlands, and Thailand.
Terminology.
The word "TexMex" (unhyphenated) was first used to abbreviate the Texas Mexican Railway, chartered in southern Texas in 1875. In the 1920s, the hyphenated form was used in American newspapers to describe Texans of Mexican ancestry.
The "Oxford English Dictionary" supplies the first-known uses in print of "Tex-Mex" in reference to food, from a 1963 article in "The New York Times Magazine", and a 1966 item in the "Great Bend" (Kansas) "Tribune". 
However, the term was used in an article in the "Binghamton" (New York) "Press" in May 1960 and a syndicated article appearing in several American newspapers on October 6th, 1960 uses the Tex-Mex label to describe a series of recipes, including chili and enchiladas 
The recipes included the suggestion of "cornmeal pancakes" in place of tortillas, which at the time were not reliably available to readers outside of the Southwest.
Diana Kennedy, an influential food authority, explained the distinctions between Mexican cuisine and Americanized Mexican food in her 1972 book "The Cuisines of Mexico". Robb Walsh of the "Houston Press" said the book "was a breakthrough cookbook, one that could have been written only by a non-Mexican. It unified Mexican cooking by transcending the nation's class divisions and treating the food of the poor with the same respect as the food of the upper classes." 
The term "Tex-Mex" also saw increasing usage in the "Los Angeles Times" from the 1970s onward while the Tex-Mex label became a part of U.S. vernacular during the late 1960s, '70s, and '80s. Adán Medrano, a chef who grew up in San Antonio, prefers to call the food "Texas Mexican," which he says was the indigenous cooking of South Texas long before the Rio Grande marked the border between Texas and Mexico.