Pop quiz: if you had to describe the Obama foreign policy in one sentence, what would you say? Not easy, is it? Back in 2008, it was pretty simple: "Not Bush." Now back then, there was something called the "Bush doctrine," which may have had a subtle meaning to those working in the administration, but as far as the public was concerned mostly meant "invading lots of countries and making everyone in the world hate us." So it was easy to imagine Obama as a breath of foreign policy fresh air. He'd use a less-bumbling combination of diplomacy, "soft power," and carefully restrained force. He'd get us out of Iraq. Things would change for the better.
But now that Obama has been president for four years, "Not Bush" has lost its relevance. Obama's actual foreign policy is too complicated to sum up easily, and probably therefore too complicated for most voters to understand. We did get out of Iraq, but things don't seem to be going too well in Afghanistan; Obama has dramatically increased the use of drone strikes, which have solved some problems and created others; though opinions of America are somewhat better, lots of people still don't like us. It's a complex picture, and in the context of an election, the Obama campaign is going to react to most foreign policy questions with, "Remember that guy Osama bin Laden? He's dead."
True enough, but this complexity has left Republicans seemingly unable to critique the Obama foreign policy.