Dan is right. Milanesas are from Argentina. I have eaten Milanesas in Mexican restaurants both north and south of the border. All I can say about it is, no two are quite the same. In Italian, a cotellete alla Milanese is a breaded veal cutlet. This suggests at least two routes to tender beef. One is to start with very young meat, and exploit its tenderness in constructing your dish. The other is to start with what may be a tough and stringy piece of meat, and hammer it into submission.
I would expect an Italian Milanese to be a very different animal from a Mexican Milanesa, and perhaps from an Argentine one as well; having never tried one, I can’t really comment. I have never tried the Italian veal variety either. When I order veal in an Italian restaurant, I usually opt for veal piccata, lemon and wine sauce with capers.
It should come as no surprise that these dishes don’t necessarily from one culture to another. Everyone knows that the French have never heard of french fries. And we should all know that in Amsterdam, you can’t get a Quarter Pounder with Cheese. It has to be a Cheeseburger Royale, because of the metric system.