“Tacos originally migrated to California and Texas in the 1920s, and only made it into scattered Mexican cookbooks written by Americans in about the 1930s”.
It amazes that it took this length of time for Mexican food to gain recognition in America. Looking back, Arellano believed that Mexican food made its American debut at the World’s Columbian Exposition in 1893. So, if we look at this timeline, it took between 30-40 years for Mexican food to rise onto the scene in America after it was initially introduced. As is the case with many new styles of food, it takes time for people of a different background to become acclimated with dishes they’re not accustomed to.
An additional wrinkle here is that Arellano says Mexican food wasn’t easily accessible across the nation until Taco Bell rose to prominence in the 1960s. Obviously, the food sold from Taco Bell is a poor and inaccurate representation of the way tacos are made in Mexico. That’s unfortunately what Americans have gravitated towards, however, while smaller ‘mom and pop’ shops with authenticity tend to be neglected because they may be unestablished or not a ‘household name’.
Arellano, Gustavo. Taco USA: How Mexican Food Conquered America (p. 53). Scribner. Kindle Edition.
Taco Literacy 
The history goes back to before either USA or Mexico existed. What unites all the peoples of the Americas is corn, and the different ways indigenous peoples of the Americas cultivated, harvested, and prepared it.
But yes, the story of Mexico and USA is old, as old as each, and even with some Spanish, French, and British influences from Europe too.
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