I see how that works. It's like if you go to a jungle river and kill one crocodile, all the others will just disappear.Mexico carrying out military operations in this country is a hypothetical that is a waste of time to consider. It won't ever happen as they can barely carry out a military operation in their own country. It doesn't matter how Mexico feels about it. They have sold their souls to the cartels. I believe you are correct in that we need to address the demand side at the same time as addressing the supply side and they can be done simultaneously. But you are woefully underestimating the effect killing cartel heads would have. Cartels aren't staffed by radicalized, brainwashed jihadists. They are staffed by rational thinking, often poor people who had no other economic options. They have a healthy fear of infinite military capability and power. We have the technology to minimize collateral damage so you are going to see how effective it can be.
It's absolutely stupid to try to stop the cartels outside the country. You can't do it and you'll only piss off everybody in the attempt.