I understand that the Great Recession would likely not strike at the same time as it otherwise would. But it still would have, as the underlying causes of deregulation of lending and the housing bubble made its arrival a when, not an if. Additionally, if it had come in 2009-10 and not 2007-08, it is still in full swing by 2011; the year of this hypothetical scenario. Similarly, the Arab Spring had underlying causes that were completely unrelated to 9/11, such as authoritarian governments, political corruption, and struggling economies. The latter may have been exaggerated by the recession, but this also was predetermined if causes were not altered.
In short, the Great Recession and Arab Spring were still going to happen because of the causes already in place, and although the exact timing would change, they would remain highly likely to happen within the 2008-11 frame. The perpetrators of a possible attack may not be al-Qaeda, but some other organization already in existence such as the one founded by Zarqawi in 1999, or another extremist group that emerges in the midst of the Arab Spring angered by America's presence in the Middle East (which was a motive of 9/11).
With all of that in mind, here is the new scenario: America has a Democratic President in 2011, likely whether or not Bush is re-elected due to a delayed recession, and economic recovery is slow. With the Arab Spring having erupted at some point in this time period, and a radical Islamist group conducting a 9/11-like event in reaction to American presence in the region, what is the aftermath of such an event? How do the 2012 elections go, and what is the reaction of the United States and its people?