It's perhaps true that the people of Manhattan are quite dense, and that a mere 3000 or so dead and a giant hole in the ground where once two tall towers sat, along with an aftermath of respiratory illness for many who tried to clean it all up, is just not quite enough to convince them of The Truth Of A Grand Existential Islamo Nazi threat.
Though there are other theories which are probably more compelling, both about New Yorkers and those who dream of wake up calls.
And as for the suspension of disbelief it would take to imagine an amassed army of said Islamo Nazis actually occupying and controlling the island of Manhattan, and the people who could imagine such a thing...
