Did you know that more than one out of every five Mexicans who are fans of Football (or American Football, as it is called down there to avoid confusion with fútbol/soccer) is a Dallas Cowboys fan as well?
To understand the appeal of the Cowboys, we have to start it all by getting a sense of history of football in Mexico. Unlike what some may think, football has a very long tradition as a college sport in Mexico dating to the 1920s and 30s, decades that saw the formation of the two most important and traditional teams in Mexico: Pumas and Burros Blancos (White donkeys). They had such a popular rivalry that some movies were shot with the sport used as a plot element (one of them being some sort of Romeo and Juliette storyline with "Romeo" being a running back for the Burros Blancos and Juliette being the cousin of the starting QB for the Pumas).
Fast forward to the end of the sixties. Tex Schramm, looking to expand the appeal of the Cowboys, caught wind of the ongoing interest for football in Mexico, and decided to expands the team's reach, by allowing some Mexican radio stations to link to the live feed provided by some Spanish-only radio stations in the U.S.. As the audience grew, a Mexican TV station requested in the early 70s the rights to air the NFL in Mexico. The NFL, determining there could be a significant market to nurture, decided to allow the station to air only NFC matches, with the hope that the competing TV consortium in the country would request the rights for the AFC. For about two years, Canal 13 (name of the station) went as the sole channel to air football in Mexico. During this time, and since the Cowboys had already gone to the Super Bowl twice, the people in charge of programming decided that the match they would air every week would involve the Cowboys, as they figured a winning team would increase the appeal of the sport to a TV audience. People got to watch every week the heroics of Roger Staubach, Randy White, Too Tall Jones, Tony Dorsett and countless others (among them two Mexican kickers: Efren Herrera and Rafael Septién), and fell in love with America's team... a love affair that continues to this day.
As a side note, two years later, Televisa (the name of the other TV consortium in Mexico) started airing AFC matches, focusing on the Steelers as their main team (remember, this was the 70s), and a rivalry was born, further fueled by three super bowls. So popular has been that rivalry in Mexico, some of the local newscasts and blogs will call any Dallas-Pittsburgh match "Mexican Bowl". It is fair to say that rivalry is far more meaningful for the Mexican fan that the ones Dallas has with the Redskins, Giants or the Eagles.