Those who want to restrict guns in America keep pushing the canard that most guns used in Mexican crimes come from the United States, such as in this AP story:
Mexico is the main hub for cocaine and other drugs entering the U.S., and the United States is the primary source of guns used in Mexico’s drug-related killings.
Despite its vigorous repetition by dishonest politicians and press, it’s not remotely true, unless 17% is considered most.
This is just an instance of the classic story of looking for your keys under the lamppost because the light is better there. U.S. law requires guns to have markings that often make it possible to trace them, so while the vast majority of Mexican crime guns can’t be traced, the tiny fraction that are successfully traced usually come from the the U.S.