1. The Bush-Cheney administration decided to conduct a war of aggression against the relatively stable country of Iraq, leaving behind hundreds of thousands dead, a destroyed infrastructure, and a government of religious zealots. This should be enough to make any sentient Iraqi believe that the United States is their enemy.
2. The Bush-Cheney administration's conduct of the war constituted one of the greatest military blunders in world history, leading Iraqis to believe that the United States is an incompetent, powerless country despite all of its military equipment. This leaves ISIL and others of its ilk with the opinion that they can do whatever they want without fear of an appropriate response from the world's only remaining superpower.
Still blaming Bush? You bet. And as long as it's his fault, I will go on blaming him.
I want to mention what was perhaps the last great military blunder in the world, the Austrian attack on Serbia.* Austria-Hungary had 12 times the population of Serbia, and after manufacturing an excuse for war in 1914 should have been able to crush the Serbian military within a few weeks, thus having their revenge for the assassination of Archduke Ferdinand; at which point the whole thing would be over, leaving little more mark on history than the Balkan wars of a few years earlier. Unfortunately, due largely to a miserable general staff and a very poorly trained army, Austria could not bring about a quick end to its attack. Had the Austro-Serbian war ended in weeks, there would not have been time for Germany, Russia and eventually France and Britain to mobilize. This might have saved 20,000,000 or so lives, and probably 50,000,000 more in World War II.
And here we are: The Bush-Cheney aggression, coupled with their incompetence at bringing it to a conclusion in the promised few months, is a very major factor in the madness we see now in the Middle East. In the great Republican tradition of making messes and leaving Democrats to clean them up, it will now fall to Obama to beat ISIS into submission, while every step that he makes or doesn't make will result in vicious attacks from the Republican party.
In a major foreign policy victory which, since it is Obama's, the mainstream press has totally ignored, Obama's use of minimal military force did in fact force ISIS to stop their advances, and turn instead to the sort of public barbarism which is such a staple of terrorist groups who have little other power. They killed an American journalist, all right, but they are now running scared of Obama- something Bush and Cheney, with their three trillion dollar aggression never accomplished.
Update: And just in case you thought I was kidding- it's now an hour or two since I wrote this, and the firestorm has started.
"Fox And Michael Hayden Try To Hold Obama Accountable For ISIS Brutality"
*The German attack on Russia in 1942-1943 certainly was a disaster for the Germans, but I don't count it as a blunder; it was defeated, but not every defeat is a blunder.