President Barack Obama, speaking in Mexico City on Friday, said the United States is responsible for much of the crime and violence in Mexico because of the demand for drugs and the illegal smuggling of guns across the southern border. … Obama acknowledged the illegal smuggling of guns into Mexico by American criminals, but did not mention the Justice Department’s Operation Fast and Furious that allowed the flow of about 2,000 U.S. guns to Mexican drug trafficking organizations. Fast and Furious began in the fall of 2009 and was halted in December 2010 after two of the weapons from the...