The US is running something like $100-200 billion through Mexico for drugs while simultaneously pumping tons of money into anti-drug policies (though, an order of magnitude or two less).

We're perfectly capable of destabilizing our own neighbors through unrealistic Puritanical policies, tyvm.

Mexico is a proxy war between US factions, as is the whole of drug trade in the Americas. It always has been.

For reference, Mexico only has a GDP of about $1 trillion, so hundreds of billions in drugs trafficking is a major economic influence on the country. The US invaded Iraq for about $100 billion per year.

Is it any surprise that giving cartels a level of funding required to wage a war, that accounts for a substantial portion of the host nation's GDP is going to mess the place up?