Serpico, The Warriors, The French Connection, Taxi Driver, Coming Home, Soldier Blue and Midnight Cowboy (Ok, so it's 1969
) are just a few that spring to mind.
When you read the reviews and analysis, it would seem that a lot of US filmmaking in the early 70s was driven or influenced by a post-Vietman imperative to re-examine basic and previously ignored aspects of American society. A lot of these films display a gritty reality and stark focus on the underbelly of America and clinically dissect it's self-image. Iconaclastic and shocking when released, time has diminished some of their impact, but nevertheless, they serve as a rude awakening from the pre-Vietman American dream.
(The above pseudo-intellectual twaddle is copyright of Mouse Productions 2003. The reproduction in whole or in part is positively encouraged. The author expressly excludes liability for any mockery received as a consequence.
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