What does "on the United States itself" mean and why does 9/11 meet that standard but not, say, the Pulse nightclub shooting?
On 9/11 there was a plan set in motion to crash a plane in to the Capitol, which only failed because of the bravery of the passengers in that plane. Incidentally, the very same Capitol self described 'patriots' broke into and vandalized last week.
So what made 9/11 have large scale was the (thwarted) plot to crash into the Capitol and the successful attack on the Pentagon? Not the 2600 killed in the WTC?
This seems like a very twisted reading to compare two not-actually-that-similar events.
Rather than engaging in the reasons for why it might be, you choose to insult my reading comprehension. Take care, and hopefully you can be more charitable to those you encounter in-person.