The United States used to be an example to the world. As a nation it used to take its founding principles seriously. That started changing during the cold war and became most obvious post-9/11.
The idea that the Constitution was an immaculate instrument forged in a gilded age of freedom, with a decline since then, is wrong. There have been bumps and missteps from the start. And in some areas, like freedom of speech, the right has been strengthened and clarified over years of jurisprudence into something that is more freedom-preserving now compared to when it was declared.
Or so the americans say. Who else ?
Of course, back then there was an obvious common enemy to point at, and the help the US provided to our country during and after WWII was still kind of fresh in the collective memory.
The cold war marked the beginning of global surveillance: the USA and other world powers launched satellites pointed at the Earth in order to constantly watch their enemies. After 9/11, the definition of "enemy" apparently expanded to include a nation's own population. Thus the 21st century is the beginning of total surveillance of all humans on Earth, not just enemy military forces.
Terrorism really is effective. America was not defeated but it a certain way it was destroyed. It abandoned all the principles it stood for in the name of national security.
See the patriot act, TSA, DHS, and other nonsense.
The terrorists won the moment we decided to live in fear.