Shot One: WMD Stockpile of chemicals. US intelligence has satellite imagery that suggests Saddam sent his stockpile to Syria, it is possible, due to the upheaval in Syria, that these chemicals have come back to Iraq - probably long time expired but still lethal.
Nut Loose - Iraqi oil, if Iraq never produced another barrel the cost of petrol at the pump would go up by no more than a cent or two per litre and probably not in the USA who don't depend on Middle Eastern oil anyway. Do you seriously think the USA would commit hundreds of thousands of men and billions of dollars to Iraq in order to save the rest of the world from a two cent rise in the price of petrol?