Jaime Daremblum writes an interesting piece on Central America for The Weekly Standard. He makes the point that Mexico is a very important U.S. trading partner.
While Mexico is beginning to get the drug violence under control, the cartels are moving their operations into the adjacent three countries: Guatemala, Honduras, and El Salvador. Central governments in those nations are less firmly established than in Mexico, thus corruption is easier to achieve.
Daremblum reports something I didn't know - we have several small special forces bases on the ground in Honduras and Guatemala. Their mission is to train local forces in counterinsurgency.