In American Sniper there is a scene showing Chris and his wife watching live TV reports of the 911. Chris seemed furious and in later scenes he was in Iraq already. Did he skip Afghanistan and was deployed straight to Iraq? Also why did the plot writer put these 2 events together? As far as I know, Iraq had nothing to do with the 911 attack.
Chris was in training at the time and he didn't get to go to Afghanistan, instead, he went to Iraq in 2003 on the mission to eliminate Osama Bin Laden and break down the two terrorist groups of al-Qaeda and the Taliban by targeting the most important of officers in the two groups, as well as the invincible Iraqan sniper.
Iraq, and its leader at the time, Saddam Hussein, was believed to have close ties to Al Qaeda, headed by Osama bin Laden. The US invasion of Iraq was based on the belief that Iraq possessed WMDs (Weapons of Mass Destruction), and that those WMDs were at the disposal of bin Laden, who was tied to 9/11.