I'm not sure the body of experience is really that deficient. We've had models that were successful (Japan, Germany post WW2) and complete failures (Afghanistan post Soviet withdrawal). We have continuing nation building projects (Balkans), and a handle on the history of the region (Lebanon, Syria, Iraq under British rule). In fact is was ba upon these experiences that Shinseki based his estimates. It was pretty obvious that it was going to take a lot of troops, time and money to turn out successfully. Given the history of the region, the role religion plays in the society, the tribalism and anti-Americanism, it was always an iffy proposition.