Bullshit! Bullshit! Bullshit! Bush is so full of bullshit, it boggles the mind.
I watched him give comments after his pep talk to the NSA (Bush Thanks NSA Employees). He says that two of the hijackers were in communication with a known al Qaeda agent overseas (true). In the speech, he claimed that 9/11 could have been prevented if the current illegal NSA spying program had been going on before 9/11.
FISA would have no - I repeat no impact on the U.S.'s ability to intercept communications between the 9/11 hijackers and al Qaeda agents overseas. FISA only requires a warrant to monitor US citizens and permanent residents.
The 9/11 hijackers were neither.