A bit silly. Of all the things causing problems for the US economy, Osama bin Laden is fairly low on the list. He's not a complete non-factor, but the entire war on terror + homeland security apparatus is a small drain compared to things like "underfunded public sector pensions" and "a decade of writing stupid home loans to morons who couldn't possibly pay 'em back" and "uncontrolled illegal immigration" and "hey did anyone actually think this whole Medicare/Medicaid thing through when we started it up" and so forth.

Or to put it another way... in August 2001 the US economy was actually looking pretty shaky. Then there was a seven-year boom.