The threat that Terrorism poses is not in the event itself but the reaction of the financial markets to that event. A major event in an American city could result in a run on the bank, thus causing a crisis of liquidity which would then melt down the system. That is what nearly every nation in the world recognized after 911. That is why Al Qaeda poses such a threat to the status Que. That is also why the USA has to respond swiftly and surely militarily to reassure the world that the status Que is still viable.