I doubt Bush would have gotten elected for a second time if it wasn't for 9/11 and I think Obama would have had a much harder time getting elected if Bush hadn't destroyed the public's opinion of the republican party.
http://en.wikipedia.org/wiki/Jack_Ryan_(Senate_candidate)#
And the major newspapers covered up the illegal wiretappings for more than a year. Originally they were going to be released just prior to the 2004 election. I contend that if they had been released, then Kerry would have won overwhelmingly. This cover-up, along with a few others, such as Abu Ghirab, lead me to have no sympathy for the struggling newspapers - they abandoned us when we needed them.
http://blog.wired.com/27bstroke6/2009/04/doj-nixed-inves.htm...
Indeed stop it and you could well kill more people (no by atroscities but by the butterfly effect etc.) - do you then go back and stop those deaths? Where does it stop? Do you go back to influence the decisions that affect every innocent life, do you constantly tweak history to ensure the maximum people "survive"?
The fact that 9/11 HAS happened means that if anyone has invented a time machine at some point in the future (or whenever) they either took the correct decision not to change history dramatically. Or they did and that was a potential consequence.
As I said below. Tampering with History itself is an unbelievably dangerous game.
But then, you in a cycle, because I am sure there are lots of past tragedies one would want to pre-empt.
Personally I would leave it as it is: harsh as it sounds, tampering with History seems a worrying path to tread...
(no reasons why you couldnt track down Osama - for example - then jump back in time to tell the US forces where he will be at XYZ date to pick him up :))
The US knew where to get Osama many times. They didn't because they didn't think that he wasn't interesting.
That's the Cassandra problem. How do you convince the US to do something about Osama before 9/11? Lots of people claim to know the future.
I mean NOW, in the modern day, find Osama then jump back a month or 2 and provide the military with the date / time / location :)
Theoretically then you are not affecting the "past" provided the US military dont arrive till after you make the jump back in time.
But to stop 9/11, you would have to track down Cheney.