Bill LeoGrande (American University) has a nice graphic showing the emphases of Southern Command in Posture Statements from 2001-2014. His main point was to show concentrated it was on criminal activity and terrorism, which is true (and which I published an article about in 2006).
Other things also pop out. One is the recent obsession with China, Iran, and Russia, which is new in its intensity. The focus on external actors didn't even arise due to 9/11 but perhaps relates more to the Iran nuclear controversy. Who knows why China comes up now--maybe if we think we're supposed to be concerned about Russia then we need to think about China too. Oddly enough, there was a little break in obsession with transnational (really meaning Islamic as opposed to drug trafficking) terrorism in the second half of the Bush presidency, which ramped back up with Obama.
FYI, if you're going to LASA then come to the roundtable I organized, where LeoGrande will be a participant.