We have been giving them military aid. We let them have their own version of the M16, and because of how much corruption there is, and how many of the cartel guys defect from the Army, it's unsurprising that they have them. The original Los Zetas were Special Forces contracted by the Gulf Cartel to do enforcement and fight their battles for them. The Zetas have since taken over from the Gulf and they are even worse. The old cartels were hateful gangs, but they at least exercised a sort of pragmatic villainy. If you didn't get involved in their business and you didn't cause problems for them, then they would leave you alone. The Zetas are unrestrained psychopaths who essentially go out and do anything they want simply because they can. They kill for no reason, they force people off their estates, they take over towns, they ride in convoys and go head to head against the official military. The sort of stuff they get up to is what you'd imagine would be restricted to 3'rd world tribal wars.
The drug war isn't going to end until Americans kick the drug habit. Yes, vegan pacifist pot smoker, even you contribute to the drug war. Who do you think grows your weed? Who do you think transports it from the fields to the city? Who do you think sells it to the local deals? Who do you think the guy who supplies your dealer is? Who do you think your dealer is? Here's a great hint: they aren't the sort of people who would risk death, mutilation, and imprisonment just to see you grin stupidly and take 4 P.M. naps. You cannot take drugs and claim to hurt nobody. A point of contention between my old roommate and I was that he claimed that unlike guns, his Marijuana never hurt anyone. Well then, what about the Drug Wars, people who drive while high and crash, that damn chronic cough I had for several months, what about really stupid decisions that kill people, what about addicts who ruin their lives, what about all the revenue it brings to the criminal elements? In contrast to drugs, almost all firearms in this country will never be involved in or connected to crime. More guns are used against crime than for crime. A gun can be used for good. A drug can only be used for escapism.
The drug cartels developed because of the U.S. Drug War and the fact that the U.S. appetite for drugs is enormous. It doesn't matter what you do; people want drugs and others are willing to fulfill that need for a price. Therefore, drugs will continue to flow. The only way to sink these criminal enterprises is to legalize drugs, put the whole industry into the eye of government regulators and the public and legitimate businessmen. Drugs are legalized, people now can get their drugs from legal sources without having to deal with cartel price gouging. Drug prices collapse. Drug gangs go under. The War On Drugs is also causing problems with the criminal justice system. The most common reason why people go to prison is a nonviolent drug offense. We are filling up our prisons with people who could be productive members of society and making the system overcrowded for the people who really ought to be in there.