Wannabe, I see where you are coming from. I don't agree, but there are elements which are true.
The fact is that 9/11 was so shocking because America is a SuperPower. Security, Intelligence, Money, Power. For a country that is THAT powerful to be brought to its knees, is phenomenal, and NO-ONE would have imagined it.
For what it's worth, I think that had the devestation been caused in the UK, it would have had a similar impact. Except of course, that we don't have buildings that are as humungous as the WTC.
The event didn't just shake America, it shook the world. Because let's face it, if they can do it there, they can do it anywhere.
If that had been, say, a poor war-torn country, then no, I don't think it would have the same coverage, impact or effect 
The real impact was that it was transcending the boundaries of the USA. It was an attack on Western Civilisation. Ruthlessly co-ordinated, meticulously planned, devestatingly effective. RIP.