It's true: in the future all restaurants wil be Taco Bell.
Cuisine evolves, it always has. What people call Chinese food in America bears little to no resemblance to any food in China. Chinese immigrants who open restaurants here for Americans have to cook different food from what they actually eat. But that doesn't mean that American Chinese food is a sham. It is the evolution of food coming from Chinese railroad workers who had no access to the ingredients they knew and developed recipes based on what was available. As they migrated to places like San Francisco, they set up restaurants and served the food they could, introducing Americans to the food developed in work camps. That was AMerican's exposure to Chinese people and Chinese cooking and it stuck.
'Mexican' food is the same way. It's Tex-mex. you have a conflation of northern Mexican food from the poorest people's of Mexico running into immigrants from Ireland, Poland, Germany and Slavik people. This turned into a new regional cuisine which was then spread and marketed abroad.
But this isn't just an American thing. It's a human thing. We just have had the benefit of a wide variety of cultures and cuisines to work with. You can get pizza in most countries around the world. It often doesn't bear close resemblance to New York pizza, which is arguably the source of American style pizza (though Chicago has their own take). Just think: the world believes that American Hamburgers are accurately represented by McDonalds. Not In'n'out, not Big Boy, not Whataburger, or Crystals, or Redline. McDonalds.
I remember going down to Juarez with a group and spending the day there. On the ride back, we saw a Taco Bell sign and we had to stop because one guy was disappointed that the whole day he didn't get to have any 'Mexican food'. BTW, I don't know about now, but 20 years ago the pizza in Juarez was pretty excellent.