And the cartoon brought up a valid point, if we mentally bring the USA down to the size of two kids, the attack becomes about equivalent to some toys falling over.
Don't get me wrong, I'm not talking about individual tragedies here, but the event seen as a whole. All expected catastrophes... did not happen. The national economy barely shrugged and internationally it was like throwing stones into the ocean, the USA did not withdraw from the world and become the next hermit kingdom, what was demonstrated was that large scale terrorism isn't as terrifying as it's been made out to be. The same goes for the bombings of London and Madrid, they happened and life went on, nothing changed in society and terrorism failed again.