This is going to be a very short review.
American Sniper is a rather promising movie, but I can't help but feel its entirety is a mixed bag, almost always ending up on the negative side of that statement.
It details the life of America's most deadly sniper, Chris Kyle, and while director Clint Eastwood does a bang-up job in the early going pacing Kyle's pre-sniper days very well, he seems to struggle with how to pace the ending, which is quite understandable as Kyle was murdered after the source autobiography as well as actual filming had actually begun. But despite this late stumble, Eastwood's direction is, on the whole, very good. I would argue he's the greatest actor-director in history (at least that I can think of while writing this sentence), and he has some truly stand-out moments, not least of which is the sandstorm scene.
Nevertheless, the film is a true and honest testament to a modern day American hero and his struggles within himself to overcome the guilt of killing some of the (albeit deserving) people he killed and to overcome the PTSD he suffered back home.
Bradley Cooper delivers a very strong performance, the best of his career (yes, even better than his outstanding Silver Linings Playbook work), and Sienna Miller is solid enough as well.
The writing is what really destroys any chances the movie has at greatness of any sort. It is essentially an American propaganda piece without an ounce of understanding of cultural differences (not that I'm trying to give any excuse for Islamic militants). Strangely I found some of Cooper's strongest moments to be when he's making up for the script's massive shortcoming's, somehow reconciling Kyle's hearty agreement with a fellow soldier's noisy and ignorant (and often vulgar) blanket denunciation of Arabs, their culture, and the entirety of the Islamic religion and its followers in one scene, and showing incredible empathy for the plights of those whose denunciation he endorsed just a minute or two earlier. He also does a wondrous job making his PTSD believable and not over the top, especially since the script has absolutely no build-up to it. Considering the script's horrendousness, Clint Eastwood's ability to at least occasionally add some sort of unifying tone is quite a feat, even if it's only, as I implied, about one-quarter of the time.