It's true terrorism wasn't a new phenomenon in 2001, but Americans saw it as 'A thing that happened elsewhere' before then.
The Nazis aren't the only nation who've ever tried to completely dominate another. Japan did it to China around the same time, France did it to Algeria, powerful nations did it to the rest of the world for all of the 19th century, the Romans did it to every culture around them.
Recommended film watching:
The Battle of Algiers
The Human Condition Part I
Army of Shadows