Juan Cole says Iraq is a failed state beyond the USA's control:

The United States military does not control Baghdad. It doesn't control the major roads leading out of the capital. It does not control the downtown area except possibly the heavily barricaded 'green zone.' It does not control the capital. The guerrillas strike at will, even at Iraqi notables who can afford American security guards (many of them e.g. ex-Navy Seals). If the US military does not control the capital of a country it conquered, then it controls nothing of importance. Ipso facto, Iraq is a failed state.