"The eruption of civil war in Iraq would have many implications for the West. It would likely:
Invite Syrian and Iranian participation, hastening the possibility of an American confrontation with those two states, with which tensions are already high.
Terminate the dream of Iraq serving as a model for other Middle Eastern countries, thus delaying the push toward elections. This will have the effect of keeping Islamists from being legitimated by the popular vote, as Hamas was just a month ago.
Reduce coalition casualties in Iraq. As noted by the Philadelphia Inquirer, "Rather than killing American soldiers, the insurgents and foreign fighters are more focused on creating civil strife that could destabilize Iraq's political process and possibly lead to outright ethnic and religious war."
Reduce Western casualties outside Iraq. A professor at the U.S. Naval Postgraduate School, Vali Nasr, notes: "Just when it looked as if Muslims across the region were putting aside their differences to unite in protest against the Danish cartoons, the attack showed that Islamic sectarianism remains the greatest challenge to peace." Put differently, when Sunni terrorists target Shiites and vice-versa, non-Muslims are less likely to be hurt.
Civil war in Iraq, in short, would be a humanitarian tragedy but not a strategic one."So agitating ethnic tensions and civil war is ok because, even though the utterly groundless and illegal US invasion caused it, it would have positive strategic implications for the US at the regional level.