Here's the bottom line:  There is no movement in southern Iraq for an independent Shi'ite state.  On the contrary, there is fear that the U.S. will do what the British did and try to break up an Arab nation so as to weaken it.  Yes, Iraq is a colonial mishmash, but as with most other Arab states, it's one where the population tends to want greater unity rather than further subdivision.  I don't know the full history and culture of Northern Ireland.  I do know the history and culture of Iraq.