This is the answer. The cartels would have to be insane to poke that particular bear. They would get crushed like a bug. IIRC they murdered a single US undercover officer in the 90s and the retaliation was so bad that they themselves handed over the perpetrators.
You are right rationality is their strongest character trait.
> They would get crushed like a bug.
Much as I despise them, I'm not so sure that would be the case. I seem to remember folks saying the same about the Taliban, and the cartels have a lot more money and high-tech kit, than the Taliban.
Asymmetric warfare is a tough gig, on all sides.