Note that in the US, we have strict stop everyone controls at the border (with Canada no less, this isn't just a Mexican border thing), at which you need to show your passport, and we have mobile border controls up to 100 miles within the border.
I used to live near a place where they frequently put the "mobile" control on an interstate in Vermont about 80 miles from the border, so I got stopped by it a lot.
Of course, I've always wondered about how useful the mobile controls are, other than for getting people used to a police state. They are not allowed to ask any US citizens for passports or proof of US citizenship; so they always ask "is everyone in this car a US citizen" and then wave you on if you say yes. When my friend, who is Malaysian, answered "no, I'm not a US citizen", they thought based on his excellent American English accent that he was joking and waved him on anyhow.
And if you're a dirty foreigner you have to have your Iris scanned, a picture taken and your fingerprints taken.
I've lived on the US/Canadian border and if they make a flip-book of all the pictures they took of me over the years it would make for a neat animated study in aging.
Really? As a Canadian who crosses that border fairly regularly, the iris & fingerprint records are only for the "Enhanced Drivers License" as far as I knew, I've crossed the border dozens of times with just my passport
Note also that people who are in this country illegally may have come here legally, and then simply stayed beyond the point that they were allowed to. That has nothing to do with border patrols, but rather whether we feel it's appropriate to aggressively police inside the country for people who may have overstayed the amount of time they were supposed to.
