Larry (LARRY THE CABLE GUY), Bill (BILL ENGVALL) and Everett (DJ QUALLS) are three friends who are also "weekend warriors," but since they're basically screw-ups, they haven't been deployed overseas with the rest of their National Guard unit. That doesn't escape the notice of Sgt. Kilgore (KEITH DAVID) who rounds them up, puts them through some basic training, and then ships off with them for Iraq.
A thunderstorm en route, however, forces their pilot to dump the plane's cargo, unknowingly sending the three men -- asleep in a humvee -- as well as Kilgore out the back end where they safely parachute down to the ground. The next morning, the three think they're in Iraq, when in reality they've landed in the middle of a Mexican desert. Believing their sergeant is dead, they bury him, and then encounter two local men they initially view as potential are insurgents, but then realize they aren't armed or dangerous.
Seeing that the Americans are armed, however, the two men lead them back to their small town where they hope they'll take care of their own form of terrorism, namely that of Carlos Santana (DANNY TREJO) and his armed banditos. The town's mayor and his lovely daughter, Maria (MARISOL NICHOLS), are happy to see the soldiers especially when they quickly scare off some of the thugs.
Once they finally realize they're not in Iraq, the three friends try to figure out what to do, all while having to contend with Kilgore who unearths himself and tracks them down, as well as Santana and his thugs who aren't pleased these interlopers are interfering with their criminal ways.