If you think the outputs of Mexican cartels stay in Mexico, you're severely underinformed. Do you know how many civilian deaths (to say nothing of human trafficking and more) are directly due to Mexican cartels?

The US absolutely has an interest in the destruction of Mexican cartels.

Also the cartels are funded and propped up by the CIA. We need them to destabilize the Mexican government, launder blood money, traffic children for our rich pedophiles and push drugs into our poor neighborhoods.