Why keep artificial borders?

David Brook's editorial today regarding the "Sunni Shiite Conflict in Iraq" is dis-heartening in it's analysis that we should of stayed until we buried the twelve hundred year old religious split in Islam. ISIS, for the Islamic State in Iraq and Syria, is Sunni and is carving out a Sunni region within Syria and Iraq.  Let them!  The Kurd's would be better off by splitting from Maliki's Shia portion of Iraq as well.  Iraq was just a region of tribes drawn out on an English map after World War I so what is the big deal that it splits up? Is it worth one more American life to keep up the fiction?