I think the seeds were planted in the pacific theater. After such a terrible surprise attack, the USA probably feels justified in preventing future attacks by all means possible. Isn't that what national security is all about? Also, cryptanalysis was highly successful in the second world war: the outcomes of many battles were determined by successful interception and decoding of enemy communications. The importance of knowing enemy secrets was proven.

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.

Americans worked overtime post-9/11 to make sure the terrorists won. We made sure to become so afraid, so terrified in daily life that we were willing to give up our freedoms.

See the patriot act, TSA, DHS, and other nonsense.

The terrorists won the moment we decided to live in fear.