I was somewhat surprised by how offended people were, "friendly" booing is a part of soccer, especially on the other side of the Atlantic. I guess Americans still aren't used to soccer enough.
As for biting the hand that feeds them, the U.S. is one of Mexico's biggest obstacles from becoming a first world country (their biggest obstacle however is their lack of infrastructure) Being that the U.S. (and Canada) made an ugly bag o' crap called NAFTA that limits Mexico's maximum wage at a rather low sum (so we can enjoy good, quality, "Made in mexico" products at good, low, prices
)