Who says it just has to be a city? What if it was flown against stockyards or other agricultural targets? That would impact us economically.
That will happen too. Don't you think that British arab moslem terrorist have brought over some nasty vials of hoof and mouth germs to spread "down on the farm"?
I think that Osama Bin Laden has an entire range of "weapons" he will release as we punish the terrorists in his end of the world.