WWII, Hitler and Pearl Harbor changed the world. If it were not for WWII there would not be a Cold War nor the creation of the military-industrial-complex. While different, the same is true with the 9/11 attacks.
9/11 created the counter-terrorism-industrial-complex. It also created an industry of so called counter-terroism analysts, speakers and authors. America was forever changed. People spoke of concentration camps. Paranoia and hysteria remains rampant.
It expanded from there. It became "emerging threats" which is a common phrase used about the South China Sea. The "eminent threat" of the Chinese Navy as we expand our naval fleets in what is simply in preparation for a war with China.
The "emerging threats" narrative is also applied elsewhere around the globe. It also includes as Donald Rumsfeld once mentioned, known unknowns. The counter-terrorism industry is prepared for things they don't even know exist.
Given time this will be and is being expanded into sub-orbital space with the newly formed Space Force as America finally takes their security into space as Reagan once dreamed with his effort in the "Star Wars program."
We also see further developments with DARPA, artificial intelligence, robotics, etc. We continue to be prepared for war with the Romulans. We are prepared for great naval battles and air to air combat. The deployment of nuclear weapons that can destroy the world.
So that's almost were we sit. Everything turned to shit after 9/11. In fact, I even was swept into the hysteria for several years. I think even Andrew Sullivan became a "counter-terrorism" expert if I'm not mistaken.