Nafta was meant to be a win-win treaty, at least for those who owned the businesses and the land. Mexico would open her doors to the import of US grain, and we would open our doors to the import of cheap manufactured products from Mexico. Wages would be lowered for US manufacturing workers, and peasants driven off the land in Mexico by falling grain prices, and all would be well with the world, as seen by people with lots of money.
So we helped the Mexicans assemble, in towns on our border, millions of incredibly poor people, working in brutal slave-labor conditions, or, by the tens of thousands, unemployed. Control of this area is what Mexican gangs fight over. Where our government would levy taxes, this drug-gang government collects protection money. The term 'drug-gang' is actually a misnomer- these are really regular gangs with drugs as one of their largest businesses, but far from their only business.
In fact, there's every reason to suspect that intimidating labor leaders might have been an early, and ongoing, role for the gangsters in Mexico. If the workers aren't cheap, the goods aren't cheap, and keeping the workforces cheap usually means intimidation, and not providing the elements of good government- education, social services, utilities and sanitation, and the maintenance of public order.
Bill Clinton and Tony Blair think this is the best way to raise the living standards of the world. I'm not so sure.