Is it any sane to keep Iraq "united"?

"Well I don't really believe that we ever were united. Present day Iraq is the old very different old states of Mosul, Baghdad and Basra put together. Before that there was never a ruler for all the states together. There always used to be one over each one of them. Empires kept coming and going, but never did they appoint one ruler over all these three states. There always was the Wali (ruler) of Baghdad and that of Mosul and that of Basra (also Najaf). Now why would that be?"
Iraqi Atheist