The Department of Defense thinks so, or at least that a political collapse is within the realm of possibility.  In fact, they think a collapse is about as likely south of the border as it is in Pakistan.  Where Islamabad’s risk comes from radical Islamist terrorists, the drug trade is what might do in Mexico:

Mexico is one of two countries that “bear consideration for a rapid and sudden collapse,” according to a report by the U.S. Joint Forces Command on worldwide security threats.

The command’s “Joint Operating Environment (JOE 2008)” report, which contains projections of global threats and potential next wars, puts Pakistan on the same level as Mexico. “In terms of worse-case scenarios for the Joint Force and indeed the world, two large and important states bear consideration for a rapid and sudden collapse: Pakistan and Mexico.

“The Mexican possibility may seem less likely, but the government, its politicians, police and judicial infrastructure are all under sustained assault and press by criminal gangs and drug cartels. How that internal conflict turns out over the next several years will have a major impact on the stability of the Mexican state. Any descent by Mexico into chaos would demand an American response based on the serious implications for homeland security alone.”

No kidding.  We’ve discussed the problems of failed states on a number of occasions and the risks they pose to national security.  To my recollection, no one has seriously gamed out what having a failed state on our border would mean.

Why the concern?  Mexico’s security forces have deteriorated sharply, and corruption has created conflicting loyalties within them.  Drug cartels have perverted the state organs of law enforcement and security, turning them into mercenaries and worse.  Earlier this week, Mexico’s government sent 2,000 troops into Juarez to quell a rising war on the streets that has already killed 35 people — since the beginning of the year.  That’s a murder every eight hours since New Years Day.  Even Mexico’s federal government can’t trust the local police.

How would the US protect itself from a warlord-ridden Mexico?  We’d have to give serious consideration to arming the southern border to a far larger extent than any time in our history.  Cross-border cooperation on drug smuggling would come to a halt, as we might find ourselves in a situation shown in the movie Traffic in which we wind up unwittingly allying with one cartel over another in the guise of official governmental contacts.  And that’s not even mentioning the opportunities for terrorist groups to exploit lawless regions for their own purposes, right on our doorstep instead of half a world away.

In fact, a failed Mexico would quickly become our primary national-security concern.  Immigration issues would become secondary, at best.