The USA didn’t have any terror attacks on that scale before 9/11 either.
But, for the most part America has been safe before and after the one isolated event of 9/11 and there's no proof that anything we've done since has made us safer (likely it's had the opposite effect by stirring up animosity).
[1] https://en.wikipedia.org/wiki/1993_World_Trade_Center_bombin...