Man... could you share some copium? Mine ran out a long time ago.
México wouldn't be more stable even if the drug cartels weren't here, do you know why?
Because we are fucking assholes; corruption, nepotism and populism would still run rampant and we (mexicans in general) would still enable them. The evidence were the last elections, the next elected president has blood in her hands among many other crimes but people didn't care as long as they get some pesos, their defendants blatantly said that they vote for her to make everyone else's life worse and to move the country to a fake communism where we no longer can vote.
So yeah... the USA might have done their part LONG AGO, but the current state of affairs has been all us, shitting on each other because fuck us.