While many Mexicans hated Americans even during the Clinton area, I would it has gotten a lot worst with the anti-immigration issues coming from the US, maybe not individually towards Americans, but just overall anti-American sentiment witnessed by the booing of Miss America, and the booing during the National Anthem during soccer matches. In general because of Bush's polices, anti-American sentiment is at a all time high in the world, it's not just Mexico.
It's true and a fact of life some Mexicans are just not going to like Gringos as they sometimes will perceive them very negatively, but I wouldn't say that's the majority of Mexicans hate Americans, I would say they want their business, however if your an American who gets ripped off in Mexico, your only going to remember the negative, and not the other times you were treated decently.
Now lets talk about the perception that many white and Asian Americans have for Mexicans, as many are so damn insulting! Off the top of my head I hear, Mexicans are all drunks, who beat their women because of machismo behavior of the Mexican men. They are all uneducated who are only capable of menial labor like picking fruit in the fields. That Mexicans commit many crimes and all the young kids are gang bangers. For the girls, they lack the ability to think long range, and are only into instant gratification, and lack the ability to reason because they lack education. They don't mine getting beat by their husbands, because that's part of their culture, They are hoes, sluts, and just plain nasty....etc etc etc. OH yes, I almost forgot " all Mexican women are the same."
You get the feeling that many Americans just simply lack respect of Mexicans to downright racist, xenophobic feelings towards them.