The United States is their primary market for drugs. A weird side effect is that Obama's efforts to close the border are working, thus narrowing down the routes across the border. This makes it a bit more competitive between the cartels. Given also the insane insistence of loose gun laws allowing "straw men" to buy guns in job lots makes the US the primary armory for the cartels. We should accept blame.
Solution: eliminate the possibility of "straw men", limit the number of weapons per sales, and legalize the primary drugs of choice. Besides, the preferred drugs of choice this generation seem to be made in the USA by pharmaceutical companies anyway.