I suspect that, as several posters have noted, there’s no one answer for “the USA” – for any given region, it probably depends on when that area actually had a significant number of Mexican immigrants (or, maybe, one really entrepreneurial one). I know that, growing up in northern Wisconsin in the 1970s and 1980s, there were very few Mexican restaurants, and the ones that did exist were places like Chi-Chis (i.e., not founded by Mexican immigrants, and not particularly authentic). At that time, there were very few Hispanics, of any heritage, in the area.
Anecdote: I’m an advertising strategist, and 20 years ago, I had a major “casual dining” restaurant chain as a client. We would do focus groups among casual dining patrons all over the country; we once did focus groups in Boston.
During the focus groups, we’d talk with the respondents about their impressions of the various big chains (Red Lobster, Olive Garden, TGI Fridays, Applebee’s, etc.), and what circumstances would lead them to choose to go to one place over another. And, in Boston, a lot of the respondents said, “We go to Chili’s when we want Mexican food.” :eek: This wasn’t just one or two respondents – this was probably half of the people we talked to. And, to call Chili’s menu “Mexican food” is a serious stretch – for one thing, they position themselves as Tex-Mex, and even at that point, it’s a highly homogenized, middle-America-friendly version of Tex-Mex food.
I’d be surprised if there weren’t any actual, authentic Mexican restaurants in Boston 20 years ago, and yeah, maybe we just had a rash of terribly uninformed respondents in those groups. Even so, it suggests that, at that time, in at least some northern cities, the impression of what a Mexican restaurant is / what Mexican food is may still have been rather uninformed.