I have to agree with Todd VanDerWerff, American Sniper’s Chris Kyle is John Rambo for the 21st century.
There's nothing inherently wrong with this. It's just that enough of the movie exists as a kind of shadow version of itself as to suggest that all involved want to question something but don't dare question the man at the center. Every time the movie pushes toward a question as simple as "Does killing over 100 people change you in some way?" it freezes up. Eastwood creates lots of dots, all over the film's landscape, but he refuses to connect even a couple of them.
Thus, Chris Kyle becomes the 21st century John Rambo, rapidly retconning a major world conflict and letting Americans know that we are still okay. Most films about the Iraq war have openly asked audiences to consider what part of America's soul was sacrificed in the process of fighting an unnecessary war. Those films' protagonists become empty machines, used up by the government. Ergo, we all have been used.
American Sniper will have none of this. Chris Kyle was a good guy. Chris Kyle was an American. Ergo, we are all good guys. The movie doesn't push or challenge viewers in any way. It doesn't bother making the conservative argument for the war, nor launching liberal attacks against it.