Everyone forgets the rise of domestic right wing terrorists through the 90s. If 9/11 did anything it was to delay it by a decade.

All their crazies got shipped off to Afghanistan and Iraq to commit war crimes there. America wasn't actively engaged in war since withdrawing from Iraq in 2011. Afghanistan was scaled back. It's no coincidence domestic issues came to the forefront over the ensuing decade.

Perhaps even the wars in the middle east trained a generation of extremists to be more violent.