I think someone DID take responsibility... His name is Osama bin Laden.
Its not that simple. Imagine if they had exact warning that this was going to happen back in say June before 9/11 and after Bush had just been in office a few months. Wouldn't EVERYONE be complaining/bitching if he:1. Had armed US Air Marshalls on all US flights.2. Put out watch lists for "Arab looking air passangers"3. Arrested 19 men who hadn't yet done anything illegal other than taking flight lessons.4. Filled the sky with F-16s patrolling possible targets over big cities.5. Forced the airlines (which are never in good financial shape) to spend millions putting locked cabin doors in the fronts of all their planes immediately.6. Attacked Afghanistan PREEMPTIVELY.7. Spent billions trying to quickly update air security and implement the "search every bag" policy, probably impossible to do in time.All of these steps taken in June could have prevented this attack. However, don't you think the outrage would have been horrendous from the right and left and middle public when...guess what, no attack happened. Bush impeached may make some of you happy, but it almost certainly would have been a serious possibility if these actions had all been taken for no apparent reason. Truth is Bush was concerned about this threat which at the time was one of many probable threats. There is still little political will from the American people to do even half of what is really necessary to prevent another similar attack. Witness the outrage over the Patriot Act which is designed to allow the FBI and CIA to cooperate and share (among other things). Hindsight is 20/20, but it serves no purpose for us to demand heads for something that for all intents and purposes could not have been prevented and was an enemy act of war.