My husband, who as you know has a career fighting islamofascists, would agree very much with your point and has argued it himself (although he uses heart disease as his example). Diseases and infections are known threats with (largely) tangible solutions, while future 9/11s are vague and unknown. Where does it make sense to put the money?

Some of the money we've spent on security has been useful as a deterrent against future attacks and some bad guys do get caught, but a lot of it has also been wasted. It wouldn't be so awful except that we spend our time having people take their shoes off at the airport and confiscating their sodas while shipping containers continue to go uninspected.

Decent diplomacy, of course, would be the soundest investment and wouldn't cost much at all.