This is several weeks old, but Peter Beinart's column on immigration and national security made a very good point. Every single politician in Washington, pro-immigration or no, claims that we need to secure our border with Mexico so that "terrorists" don't sneak in. That's one of the stated rationales that restrictionists offer for wanting to build a wall and militarize our border, but even people like Ted Kennedy argue that our porous Mexican border "directly threatens national security."
Yet as Beinart notes, potential terrorists are really, really unlikely to make the dangerous trek across the hot desert to enter the United States through the Mexican border, especially when they can just do what they've always done and walk in through the even-more-porous Canadian border. Or they can do what the 9/11 hijackers did and simply enter the country on student visas. Whatever the solution might beBeinart suggests national ID cardsit's not a Berlin-style wall along the southern border.
Meanwhile, if someone wanted to sneak, say, some sort of nuclear device into this country, why go through Mexico? They could always just ship it in a cargo container, seeing as how our ports are totally unsecured and the ruling party in Washington has time and time again scotched proposals to pay for more security. Normally when this topic comes up I encourage everyone to read John Mueller's essay on how the threat of terrorism is fairly overblown (at least unless we do something crazy in responselike militarize our southern border), but even those who want to obsess about it should at least note that the Mexican border ranks relatively low on the list of our security concerns.