The sensational aspect of 9-11 was surly devastating and traumatic to the national psyche, the visibility and media aspects of which only further augmented the shock, coupled with it having happened in a country not used to such violence and carnage on its own soil. Amen. (Even if, because of TV, the shock was felt on the streets of Belgium, just as it was on those of Arkansas).
I think what you don't consider, however, (apart from the universality of the event) is that there are tragedies all around the world that have involved even more deaths, which are given less media attention, if any, in places where the people suffer and live in conditions far worse than in the US on a daily basis. Silent voices living in less "innocent" and "important" places, too pitiful and insignificant within the global geopolitical arena, or else victims of it, for us to often take notice. The horror of Sept. 11 and the "personality" of Osama bin Laden offered thus great, though tragic, examples of how American was now at one with all those silent, suffering voices. With the weak and shattered of the planet.
I have always thought that 9-11 should have been call to serious reflection: about society, the world, history and our place and force within it. Yet it was merely turned into an instrument of state propaganda and fear, to be able to put into effect plans that were already being discussed by the neo-cons in the New American Century since the 90's. And their power of persuasion was far more compelling and authoritative over the masses, than a desire for a more sober contemplation and course of action not based wholly on economic interests.
That this was indeed the case, was evidenced in the all the emotional young "party-goers" wrapped in US flags chanting "USA! USA! USA!", rather than a simple bow of the head for those who perished on an infamous date and for all those who have died since, the colossal sums that have been spent, in the name of ideology, fanaticism, interests - on both sides of the fence.
Also having the hordes chant for the death of the enemy in the West, is like the Islamic mobs burning US flags and images of the president: the flip side of the same coin. Apart from not demonstrating the tasteful composure befiting of the civilized, it is barbaric and voodoo.