re: How many
Afganistan was the home base of al Qaeda and the site of its training camps. The government of Afghanistan at the time fully supported al Qaeda. That some of the hijackers were born in Saudi Arabia is so mind-bogglingly irrelevant, except insofar as it greatly aided al Qaeda in getting visas, that your continuous obsession with it is either the sign of overly simple thought processes, or more likely, attempts to keep deflecting the point.
The attack was planned in Germany, too. Should we have attacked Germany?