In real life, of course, two strong players won't be fighting each other on command of a weakling. It just doesn't happen this way. Cartels want access to the market - which is people. Cartels have no use of the US government in any way, shape or form. ISIS fights against that government, distracting it from border control (a difficult task, considering that border control is nonexistent.) Cartels and ISIS are natural allies.
My guess is the cartel members would probably be able to switch to muzzie, at least outwardly.
Cartels and ISIS are both members of Carroll Quigley's The Pakistani-Peruvian Axis.