The Last Samauri - The “bad guys” are American diplomats and military advisors, including Cruise’s character’s former cavalry commander.
Also, technically any film about the American Civil War.
Last samurai?
Maybe this isn’t quite in line with the thread, but “Southern Comfort” has an unusual, post-Vietnam premise. American National Guardsmen find themselves pitted against angry Cajuns in the swamps of Louisiana (the Cajuns are depicted as some sort of uncontacted wilderness people).
http://www.imdb.com/title/tt0083111/
Maybe this isn’t quite in line with the thread, but “Southern Comfort” has an unusual, post-Vietnam premise. American National Guardsmen find themselves pitted against angry Cajuns in the swamps of Louisiana (the Cajuns are depicted as some sort of uncontacted wilderness people).