One of my main problems with illegal immigrants is their attitudes towards the US vs those of legal immigrants (generally). Legal immigrants like America. Illegal immigrants like their countries and are only interested in using America.
The people who are willing to put in the time and effort to become legal citizens seem to give a shit. They are American citizens, and they achieved that because they cared enough to. They put American flag stickers on their (insured) cars and celebrate the 4th of July with the rest of the country. They're fucking proud of it. They might have pride in their home country as well, but they came here because it's better here and they not only accept but embrace that fact. You ask them what they are, they say "I am an American!"
Illegals generally seem to just not give a shit. They're not Americans, they're _____. They cane here because they heard thatthey can make x amount of money here and send it home, that here they can get free health care and education, they don't care to contribute anything to the country (like taxes), they're fucking leaches. You ask them what they are, they say "I am a Mehican!" Because that's what they identify themselves as. These are the assholes who celebrate Cinco de Mayo like it's the best day of the year and tell their kids they don't have to stand for the Pledge of Allegiance in school or give half a second's thought to the 4th of July. They hang little flags on their mirrors from some other country so that everybody else can see.
In short, there's a critical difference in how they self-identify.