I think most people simply want to see Mexicans coming here DOCUMENTED and LEGALLY like all other immigrants. I don't give a crap if the immigrant is from India, Russia, Germany, Mexico, Austrlia or Iceland, as long as they come here legally. Just because they share a border with us, does not give them the right to walk across it when they see fit.
I would think if China were bringing their citizens over on Navy ships and dropping them off in international waters with rafts to take them to shore, we would rightfully see that as an invasion. However, when the Mexican government prints guides to making it to America, those people are just poor people looking for work, and they are to be helped.
And this whole 'they are here for jobs that no one will take' is crap, while we have an unemployment rate. Maybe when all Americans have jobs, we can concern ourselves with providing jobs for illegals.
As far as an American being extradited, he should have thought about that before he killed the police in Mexico. I'd send someone to ensure he was getting a fair hearing, and if so, then he's gonna have to deal with the penalties. And yes, if the Mexicans wanted to send someone to ensure that this guy was getting a fair trial, I'd let them.