Mexico: Organized Crime and Drug Trafficking Organizations [Updated December 20, 2019] [open pdf - 1MB]
From the Summary: "Mexican drug trafficking organizations (DTOs) pose the greatest crime threat to the United States and have 'the greatest drug trafficking influence,' according to the annual U.S. Drug Enforcement Administration's (DEA's) 'National Drug Threat Assessment'. These organizations work across the Western Hemisphere and globally. They are involved in extensive money laundering, bribery, gun trafficking, and corruption, and they cause Mexico's homicide rates to spike. They produce and traffic illicit drugs into the United States, including heroin, methamphetamine, marijuana, and powerful synthetic opioids such as fentanyl, and they traffic South American cocaine. Over the past decade, Congress has held numerous hearings addressing violence in Mexico, U.S. counternarcotics assistance, and border security issues."
CRS Report for Congress, R41576
Congressional Research Service: https://crsreports.congress.gov/