It appears that the terrorists have already scared NY & DC enough. I suspect they want to scare the rest of the country before they hit NY again. Since they seem to want to target the U.S. and World economy you might think they might want to hit an another economic target, say an oil reserve, a port, or a west coast or mid-west financial center?
Do you really think that most Americans live in fear today and are easily coaxed into terror by the announcements by our government? Did you know that the recent threats were discovered by the Canadian government who shared the info with us? I severely doubt our government used the announcements for political purposes.