That happens because you have in USA mexicans with no education, pure ignorants that can't even write in spanish. They make americans think that we all eat chimichangas and burritos: I'm from Mexico, I live in Mexico, I have visited just one time USA and have ever eaten that shit you/they call "chimichanga". Keep all those ignorants there cleaning pools, we don't need them back.
The generalisation you're doing we also as mexicans could do it by visiting Chapala in Jalisco, full of old retired americans that came here because their pension is not well paid enough to live within the USA, so they come to Mexico to spend in prostitutes and drugs, they don't speak even spanish, they don't have a beneficial role in our economy. Many young americans come here to "study" in a six-month exchange. You don't need to be a genius to note they're not precisely the type of american that will study at MIT (full of chinese and indians). They come to Mexico to buy cheap alcohol (is cheap for them), drugs and eat cheap food.
It could be disgusting for you to see and hear mexicans in your country to talk, smell and eat like that, but it is also disguting for some of us see your compatriots to behave like that. Not all mexicans talk, eat or smell like that, some of us are middle class studied mexicans. Don't generalise, we don't do it.