From an article on CNN.com today:
The Mexican cartels, the report says, are “the single greatest drug trafficking threat to the United States.” The Mexican organizations have operations in every region of the United States and are expanding into more rural and suburban areas. … They’ve also stepped up cooperation with U.S. street and prison gangs for distribution.
According to Michael T. Walther, director of the Justice Department’s National Drug Intelligence Center, which produced the report. “The economic cost alone is estimated at nearly $215 billion annually.”
Note that this compares with the annual direct costs of the wars in Iraq and Afghanistan. So while we’re off in those places, guess what’s happening in our own back yard.
More than 2,500 people were killed in drug-related violence in Ciudad Juarez (across the Rio Grande River from El Paso) last year. That’s in one city, right across our border, and only the murders we know about.
With this amount of money at stake, and with the level of violence that the Mexican drug cartels routinely employ, we might rephrase the National Drug Threat Assessment 2010 report’s conclusion as:
The Mexican cartels, the report says, are “the single greatest threat to the United States.”
We have to choose where to use our limited resources, and our survival as a free and democratic country rests upon our choosing wisely.
Slightly East of New 
It’s a tautology for the DoJ to state that the Mexican cartels are the top “drug trafficking threat” to the U.S., as the majority of international IMPORTED narcotic volume makes at least a transport stop down south (this was not always the case).
When one considers the very broad criminal and RICO authority assumed by Federal Law Enforcement over the last couple of decades, and the ever increasing percentage of the State and Federal prison system given over to housing “prohibition” inmates, it should be immediately clear WHY the Mexican Cartels have spread so deeply across the entire U.S…. American mid-level management and logistical support of the business is difficult to maintain north of the border due to the police. But because U.S. Federal Law Enforcement is unable to extend it’s mandate into Mexico, the trade-off has been a broad boost across all traditional areas of organized crime in favor of “off shore” cartels (whom also benefit from economics of scale).
Of course Washington’s answer is breathless calls to the rest of the Country declaring Mexico a “failed State” in need of U.S. Federal intervention! As this solution allows the beltway Bureaucracies change not one iota of Domestic Policy, nor revisit intrusive and demonstrably ineffectual and broadly HARMFUL practices, it’s the obvious choice for a Federal establishment determined to expand at the rest of the Republics expense into all areas of it’s citizens lives until the end of Time.
Given the decriminalization referendum coming up in California (and as Chet notes), it seems to me that States are going to have to weigh their own dedication to Prohibition against the ever increasing costs burdening their OWN budgets, and to stand off the Beltway anti-drug crusaders who’ll never admit defeat as long as the price, fiscally and socially, can be dumped off to the States without a proportionate say in enforcement policy.
Best,
A. Scott Crawford