I believe Treason may actually better describe some of the crimes committed. Covertly providing thousands of weapons to a paramilitary force (drug cartel armies) in a neighoring nation which is hostile to that nation and our own. What would you call that?
I think there are far more instances of undermining and subverting the rule of law than of giving aid and comfort to the enemy. It would also be hard to cast Mexico as an enemy nation, legally speaking.