The US response to 9/11 has been a major contributor to America’s current economic malaise. The most economically costly decision post 9/11 was not whether to attack Iraq and Afghanistan, but how to pay for the ensuing conflicts and the related increases in defense and homeland security.
Bilmes, Linda J. "US Response to 9/11 Contributed to Causes of Current Debt Crisis." Christian Science Monitor, September 9, 2011.