I don't think the physical impact of 9/11 was that important. 3000 or so lives is nothing in the grand scheme of things.
The main immediate impact of 9/11 was demonstrating the USA was vulnerable. Before, they always managed to do their fighting in other countries.
As a result 1) the USA had a serious need to prove their power. They received a challenge which could not stay unanswered. 2) Europe and the 1st world in general tried to let the US kick around and prove themselves, without starting a world war, and without being dragged into it themselves. They all had similar moments in their own history, and understood how other nations would just not care as much as the receiving nation did. 3) The moslim world saw their biggest enemy receive a kick in the balls, and loved it. It was a great morale booster for them. The US could be hurt.
Long term impact was reducing the values of the enlightenment and western civilization. The US was seen torturing random people, starting a war against the wrong enemy, and limiting all kinds of freedom while claiming to be still free. They lost claims to moral superiority almost anywhere. The overton window shifted away from 'everyone has rights' and towards 'might makes right'.
The main immediate impact of 9/11 was demonstrating the USA was vulnerable. Before, they always managed to do their fighting in other countries.
As a result 1) the USA had a serious need to prove their power. They received a challenge which could not stay unanswered. 2) Europe and the 1st world in general tried to let the US kick around and prove themselves, without starting a world war, and without being dragged into it themselves. They all had similar moments in their own history, and understood how other nations would just not care as much as the receiving nation did. 3) The moslim world saw their biggest enemy receive a kick in the balls, and loved it. It was a great morale booster for them. The US could be hurt.
Long term impact was reducing the values of the enlightenment and western civilization. The US was seen torturing random people, starting a war against the wrong enemy, and limiting all kinds of freedom while claiming to be still free. They lost claims to moral superiority almost anywhere. The overton window shifted away from 'everyone has rights' and towards 'might makes right'.