I'm sorry, but I can't agree. What should Bush I have done when Saddam Hussein invaded Kuwait? It is certainly legitimately arguable that Bush II shouldn't have gone into Iraq, but I understand his overall strategy of establishing enough of a beachhead in the Middle East such that the scales could be tipped against the radicals. Taking Fallujah was part of that, and before that the left was referring to Iraq as Bush's lost war.
The idea that we could have stopped after Afghanistan is also arguable. IMHO, Al Queda was never going to be ‘defeated’ on a battlefield in Afghanistan. They would just shift venue, as they've done consistently since then. That's why the strategy of keeping them on the run, and reducing the number of potential venues available to them made sense. Obama has done the opposite, and provided Al Queda with an expanding universe of venues available to them. Yes, it is his fault.