The United States Marine Corps, commonly abbreviated as USMC, was formerly a branch of the United States Armed Forces responsible for conducting amphibious landings. In a sense, they serve as the predecessor to the United States Civilization Preservation Force. During the Third World War, the Marine Corps launched a full scale coastal invasion on China before the nukes hit. A group of them crashed into the city of Osaka, Japan, after EMP waves took down their ship. They don't exist after the events of After the Flash 2, to our knowledge, if only in tiny remnants and descendants of survivors. You can see their former equipment all over the wasteland. Track Town in ATF 3 was built by a crashed UR-22, one of their many vehicles.
What was left of the United States Marine Corps is now mostly in the hands of the United States Civilization Preservation Force. As shown in games, they have pre-war technology and locations. They have UR-22s for supplies, they have a US Coast Guard base in Rockport, FL. The USMC is now almost (if not completely) extinct. In ATF 5, you can see tanks and ships on the Beach Overpass, and also a warship in the dried out desert of an ocean behind Crane Town, which can be explored. There is also a small place to stay in the tower of a bank, which can be easily spotted because of the UR-22 sticking out of it.
Equipment: Light weapons
ATF 2: USMC Camp
ATF 5: Beach Overpass
In ATF: Osaka Reimagined, the USMC have their own startup screen, depicting of a crashed UR-22 squad with a few surviving USMC