From the U. S. State Department:
The Department of State warns U.S. citizens against all but essential travel to Iraq given the security situation. Travel within Iraq remains dangerous. This Travel Warning replaces the Travel Warning dated January 19, 2012, to update information on security incidents and to remind U.S. citizens of ongoing security concerns for U.S. citizens in Iraq, including kidnapping and terrorist violence. The United States completed its withdrawal of military forces from Iraq as of December 31, 2011. The ability of the Embassy to respond to situations where U.S. citizens face difficulty, including arrests, is extremely limited.
U.S. State Department Warning