Before I begin, be aware that I don’t have a dog in this fight but I have to point out, that in the interests of fairness, that 9/11 will probably be remembered in future more for it’s publicity value than anything else. Callous? Possibly, and I’m sorry if it appears that way - but we need to stay balanced here. In pure “military” terms of effectiveness, Pearl Harbour was way more damaging in the context of how it hampered America’s ability to prosecute military missions in the Pacific rim.
And in terms of sheer, massive brute force on a hitherto unknown scale, well 9/11 absolutely pales into insignificance compared to the 1941 assault on Russia by the Wermacht. The seige of Stalingrad and all that.
As I said, no disrespect to the victims of 9/11 and their families - but it has to be said, it was a very staged affair - as in the eyes of the world watching, and the symbolic targets chosen etc. It was a punch straight in the middle of the USA’s face - but it was far, far from being a crippling blow. What made 9/11 so amazingly paramount in the world’s collective consciousness was the extraordinary way it was all caught on camera in real time, and the way it was so localised in very small regions and thereupon compartmentalised by the media. Also, it took place in a completely unsuspecting and peaceful environment - in full glare of the world’s camera’s - and that amplified it’s impact.
However, the march of the Japanese Imperial Army through Malaysia and Singapore was far more devastating. As was the blitzkreig of Germany through Poland in 1939 etc. In these contexts, 9/11 was a strictly amateur affair which had an extraordinary bang for buck payoff - but it was nonetheless still a small affair.