Columbine wasn't the first school shooting[0], and 9/11 wasn't the first terrorist attack.
[0] https://en.wikipedia.org/wiki/List_of_attacks_related_to_sec... (The list begins with an incident in 1853)
[0] https://en.wikipedia.org/wiki/List_of_attacks_related_to_sec... (The list begins with an incident in 1853)
9/11 had a profound effect on how the US deals with terrorism, threats of terrorism or even just brown people.
Certainly not the first, but probably the events with the most lasting effects.
(why do you hate america)