Those who think, "Gosh if we'd only hung around a bit while longer ISIS never would have been a thing", are fooling themselves.
Iraq is a country made up of three very different groups of people, the sunnis hate the shiites and they both hate the kurds and they all want each other dead.
If it wasn't for the interference of western powers what we call Iraq would be three different states.
Hate Saddam all you want and I agree he was a vile horrible person as was the government he led but he kept the peace, the moment you removed the man who kept the peace ISIS or something like it was inevitable. These three groups have hated each other for centuries, attempting to make them work together will never work until they want to work together, we haven't reached that point.
When we killed Saddam we created a vacuum of power, it was inevitable that someone was going to take it's place. And just like we were wrong with the hilarious, "they will welcome us in the streets" we were wrong that we were somehow going to westernize them.
The west created the current power structure in Iran in the early 50's, the west is also responsible for the current power structure in Iraq now.
At some point we will learn to stop treating the rest of the world as pawns.