As a citizen of the US, I prefer to talk about my own country, since I have more historical context. And 9/11 was a one-time event that hasn't and can't happen again, now that we've done things like reinforce pilot's doors. Removing outliers is a pretty common thing.

Furthermore, it makes sense to start post-9/11 since "we're in a different world now" and all that rhetoric that politicians have been spewing since. This is about today's political context, where 9-11 was the defining moment.