OBL's objective wasn't to dominate 300 million Americans, his objective was to do enough to enrage Americans, provoking us into committing wholesale indiscriminate revenge attacks- atrocities- on random muslims throughout this country and abroad which would then make regular muslims so fearful of persecution they would drop their religious, ideological and national differences, get off their apathetic butts and unify as one angry international movement, the Ummah, under his influence. It would have worked except that Americans are disinclined to behave like tribal middle easterners seeking revenge against an entire opposing tribe down to the last child, and more inclined to pursuing the actual individual perps. The average muslim didn't become convinced he and his family would be targeted by mobs of rioting Americans, which meant OBL didn't get as many indignant paranoid muslim recruits as he hoped for in the west.
Maybe Plan B was to get a sympathizer in office and use him to back the rise of this Ummah, as Obama seems to be doing.