Doing a cost-benefit analysis on a war is awfully hard. There are just too many what-ifs. But the cost of invading and occupying Iraq has been staggeringly high — whether you believe the $3 trillion figure of economists Linda Bilmes and Joseph Stiglitz or side with the Congressional Budget Office estimate of a mere trillion or two. It's the biggest part of the explanation for the yawning Bush-era budget deficits. So even if you think the war did bring benefits to the U.S., they would have to be pretty gigantic to justify the cost.