Recently, on the CBS Today Show, Lara Logan, CBS new Mexico City, interviewed Hillary Clinton. Mrs. Clinton said,
"We have to recognize and accept, uh, that the demand for drugs in the United States drives them north, and the guns that are used by the drug cartels against the police and the military, uh, 90 percent of them come from America."
See this YouTube video.
I will agree with Mrs. Clinton that the demand for drugs is our contribution. However, most of these drugs can be produced for pennies, so the huge amounts of money involved is the result of several governments' policy of criminalizing these substances.
As for the ridiculous claim about "90 percent of [the guns] coming from the US", the fact is that the most powerful weapons the cartels are using (rocket launchers, automatic weapons) can't be purchased in any US gun store, and there has been no case of large-scale weapon smuggling south across the US/Mexico border.
Consider this. Juarez is one of the 'murder capitals' of the world, while El Paso, Texas, just across the river, has recently been named the number 1 safest large city in the US. The difference? US citizens have the right to keep and bear arms, and can defend their own homes against criminals. Mexican citizens don't.