The clearest illustration of the mess seen by senior officers was that seven recently retired 3 & 4 star generals turned down an invitation the be Army Cheif of Staff until finally Gen. Shoomaker accepted. He was the eighth invitee to the ball. Those other seven didn't want to be thrown that ball of glue with Rumsfeld's mess stuck to it.
We had a window of opportunity to secure Iraq but Rumsfeld stood by and quipped that memorable axiom that sometimes democracy is messy - among others that avoided the scene on the ground.
There is no one other than the president and his people who are responsible for the current intractable situation, trying to casually pass it off to any previous administration is an admission of culpability and an exercise in futility.
What would have prevented this insurgency? I am not opposed to the idea that some things should have been done differently. I just don't know how this could have been avoided. There are rabid jihadists throughout the region, and they chose to fight this process. I am open to hear what ideas you have, as it sounds like you have a good understanding of the situation.