9/11 changed a lot of things, especially for the USA. It affected the global economy as the US economy drives a lot of things, it affected our economy horribly (as we just had started dealing with the internet bust), and from that day forth, the whole concept of 'terrorism' was redefined.

This is a good and bad thing. It's good that we no longer think "that happens to other countries" or "that's what other people go through" and that we're taking a lot more precautionary steps towards being more secure, even if it won't work because there's simply too much ground to cover and we, as a country allowing anything to go, have been too lax in security for the past God knows how many years...

It's bad because now businesses are still using "9/11" as an excuse to "cut costs", further hamstringing the economy by emptying people into an already vaporized job market, all the while still spending tons of money on their political frontends who'll never take a pay cut in their natural life. It's bad because we're sacrificing our "rights" for "security" and the minute we do that, we don't deserve either (someone way more important and famous said that, hehe).