Well of course the bottom line is, if you are going to put a bunch of different tribes (think clans if it works better for you), religions, languages and so forth together in a set of boundaries and say to them: You are now a country, hey, they are not likely to be successful at being a country. Just shows that all the brilliance in the world cannot find the right solutions for sets of peoples in situations where the culture is unknown and totally foreign to the inventors of the new countries. And those who think they CAN do this, from their outsiders point of view, are ARROGANT, to say the least.
So we went into Iraq with a plan only to conquer the small country and topple Saddam. We did. In a hurry. Then, still with no plan, Bush allowed a guy named Paul something to set up the new government. He decided to ban all members of the Baathist Party. Sort of like banning all Nazis or all Communists. Or, for that matter, all Tories, Labor Party members, Democrats, or Republicans. Doesn't matter; the thing is, you HAD to be a member of that party to hold a job in Saddam's Iraq. So when that Paul fired them all, there was no one to run the army, the police, the fire department, the library, the museum, the whole cotton picking government! And no one to teach the Shites who DID want the jobs (well, the Sunnis were not very happy about not getting paychecks any longer and wanted their jobs back, but could not get them and a huge number left the country outright) even in the matter of picking up the trash!
It all went downhill from there and factional war broke out big time. Again, Arrogance of thinking you know all the answers concerning a totally different culture. We, and any other nation, should always utilize experts in the part of the world we are trying to deal with. Just plain old common sense.