Few if any under 20 years old can properly answered "what happened on Dec 7", unless they are currently in the Navy.
30 years from now, 9-11 will be meaningless too.
As many in our generation have forgotten other equally important commemorations. Even with the modern lost cause movement, most people can’t remember any of the dates that used to be fervently remembered in the years after the American civil war. Or that Veterans Day used to be the celebration of Armistice Day from WW1 and had to be rescued from the dustbin of America’s short attention span by rebranding it to the super-holiday we have now (albeit an important one.)
Most Americans think that the Pearl Harbor attack was the only time the USA was invaded, having presumably been taught that somewhere. Never mind the other Pacific territories that were attacked and/or invaded during WW2 including Alaska. “But Hawaii was a state!” they say. Um, no it wasn’t. The War of 1812, Spanish American War, the Border War, incursions during the Mexican Revolution...never mind terrorist attacks.
Not including virus pandemics from Christopher Columbus through today, or season-long droughts causing famine, I believe the single event that killed the most US Americans was the Galveston Hurricane of 1900. Not that well known or at least regularly remembered outside the local region.
Our nation's capital was attacked, occupied, and partially burned, a fair portion of the state of Massachusetts in what is now Maine was occupied under martial law, and some think that - outside of the civil war - our little experiment in republican democracy came the closest to ending...in 1813-1815. We have the
Star Spangled Banner, yes, and every Tennessee middle schooler (ironically) learns about the Battle of New Orleans and Andrew Jackson's part in it, but who remembers June 18, or December 23, or August 24 these days?
Not minimizing the impact or honor of those who were there on December 7, or who served in WW2. But I was originally trained as a historian and I think about how society evaluates tragedy fairly often.