I think a good argument can be made 9-11 wouldn't have happened.
I believe OBL and al-Qaeda were regarded by the Bushies as a Clinton thing and they were oblivious to all matters Clinton. There was a real antipathy toward Clinton's programs and concerns. With the Clinton Administration's experience with those scoundrels, I believe Gore would have been paying attention to the kind of information and warnings they were getting.
Bush and Ashcroft were busily cutting Clinton's counterterrorism budget. Interestingly enough, while Rice said the warnings and information "didn't rise to the level of concern", she has never, to my knowledge, said what she was watching, what had risen to the level.