Older 80's 90's Movie about a highly specialized M1 Abrams Tank - whats the name of it?

i saw this movie several times as a kid,  the best thing i can remember about it was it was a highly specialized version of the famous US Military M1 Abrams.   it featured missiles, and a one of a kind "Vulcan Air Defense System" of M61 Vulcan 20mm Gatling guns.  

The only scenes i remember enough was the two ending scenes.  

A long drawn out battle between some kind of warlord or drug cartel leader and his attack gunship helicopter, disabled the Vulcans to shoot down the helicopter, so they drove up a crushed vehicle against a broken wall,  and fired the main 120mm cannon at the helicopter,  destroying it.    the closing scene was that of one of the people involved in the Tank program driving up to a US Border Checkpoint:  "Can i help you? Yes,  i am a US Military service member, im coming back into the United States.   Oh,  okay,  are you bringing anything into the country you need to declare?    ....... Only that.......... " and points at the Abrams rolling up to the checkpoint, and with a bewildered look, the CBP Officer waives them through.  cut to end credits. 


Does ANYONE know the name of this movie?  i have been looking for it for nearly a decade and cannot scrounge up enough resources to find it.