I haven’t watched American Sniper, but from the trailer – and just knowing it’s a Hollywood movie – I assume it’s presented as “apolitical”, and the main character as a slightly conflicted hero.
If that’s the case, what’s left out is quite glaring: He participated in illegal wars, mainly created to serve corporate (and political) interests. And he, most likely, saw himself as serving his country, and doing his job. Which may be true, but is secondary to him choosing to be an active participant in very questionable foreign policies. The US foreign policies and military actions may well create more enemies and terrorists than they are preventing or getting rid of, and I wouldn’t be surprised if that too is left out of this movie.
By leaving these things out, the US movie producers are doing their job, which is (a) to make money, and (b) not question the actions of the US government in any serious way. (If they do so, they mostly focus on more harmless fringe issues.)