Did our parents (in many cases grandparents) forget Pearl Harbor? Before that was the SS Lusitania & the Zimmerman Telegram. Before that was the USS Maine and the Alamo and the shot heard ‘round the world.
9/11 was unforgettable. I woke up just in time to see the second plane crashing into the tower on the screen behind Peter Jennings. So hard for your mind to process such shocking events.
There was a time when anniversaries of such events were marked with some sort of observance. Future generations also learned about them in school.
Today, these events are largely ignored. In some schools history isn’t even taught, or if it is, it is spun by teachers indoctrinated by communists. 9/11 is now the fault of the US and the Muslims are peaceable folks who mean us no harm.