There was a movie involving the U.S. military being deployed to major U.S. cities for "training" while a coup take place in the president was forced to resign. The plot was thwarted at the end. It would have been from the late 90's, early 2000s.

Sounds like xXx State of the Union 2005 (http://www.imdb.com/title/tt0329774/) but the they wanted to kill the President and VP, thus taking power through succession.