There has historically been tension between the US and Mexico. Don’t forget that we invaded Mexico, and among their national heroes are six cadets who leaped off a tower rather than be captured by the Americans...and that a number of Irish Americans defected to the Mexican side.
But in practice, most Mexicans, once you get south of the border areas, just want to have a functioning country and are fine with Americans as long as Americans don’t do what the German tourists do (snap their fingers and yell “wapido, wapido” - rapido, rapido with a German accent - at the waiters).
But I do think we have to remember this. Going to another country can sometimes be a matter of survival, whether economic or political (and a lot of these illegals in vans are not Mexicans, incidentally), and I thought the comments on this thread were disgusting.