I think it is pretty strong to suggest that 9/11 was the worst attack on US soil ever without further justification. During the Battle of Gettysburg, for example, more than 7,000 soldiers died after Lee's army attacked the US army. The Attack on Pearl Harbor might also be in contention, depending on how severely you rate the crippling of the US Pacific Fleet.
I think it is pretty strong to suggest that 9/11 was the worst attack on US soil ever without further justification. During the Battle of Gettysburg, for example, more than 7,000 soldiers died after Lee's army attacked the US army. The Attack on Pearl Harbor might also be in contention, depending on how severely you rate the crippling of the US Pacific Fleet.