The threat of terrorism changed politics forever[1]. The bar for military intervention was lowered significantly. The Patriot Act in the US by itself changed global life. Privacy diminished under the guise of keeping everyone safe. Airport security theatre is just a small visible part, but the attitude change toward monitoring the public is the most significant change. In the UK and the US[2] the number of CCTV cameras ballooned since 2001. We take surveillance for granted now, I guess you don't really think about that though.

[1] https://www.aclu.org/other/top-ten-abuses-power-911 [2] http://www.nbcnews.com/id/44163852/ns/business-us_business/t...