From the Document: "United States Southern Command (SOUTHCOM), headquartered in Miami, FL, was officially established in 1963. Prior to that, U.S. military elements in the Western hemisphere had been organized under the U.S. Caribbean Defense Command. SOUTHCOM's area of responsibility (AOR) begins at the southern Mexican border and contains the remaining elements of Central and South America, adjacent Atlantic and Pacific waters, as well as the Caribbean Sea, ultimately encompassing 31 countries and 16 dependencies and areas of special sovereignty. The region represents about one-sixth of the landmass of the world assigned to regional unified commands. SOUTHCOM is led by U.S. Navy Admiral Craig S. Faller."
CRS In Focus, IF11464
Congressional Research Service: https://crsreports.congress.gov/