I mean, "purely indigenous" foods also have influences that postdate 1492 for the same reason that "purely Chinese" food might still use peppers, because actually purity is not real

Yea I just mean that Tex-Mex is kind of its own thing within the canon of Hispanophone North American foods.

Like imo it has the same relationship to Mexican food as Punjabi food to Indian food (highly localized regional variation from the borderlands that due to the vagaries of empire became a dominant form in the metropole)