If you don't know what FUBAR means...
...then I suppose it's a perfectly family-friendly acronym, and if you do, well, I can't do any more damage to your impressionable mind. And there's no doubt, Iraq is FUBAR.
Ian Welsh has a list of some reasons over at BOPnews. It's arguably incomplete, but certainly worth a review. It's a long post, but I recommend a thorough reading. Here are his sub-heads...
Threatening Iran and Syria
The Immediate Post War Period
The Coalition Provisional Authority
Chalabi : To weak to rule, too corrupt to serve
Disbanding the Army and the Secret Police
Failing to control weapons and munitions stockpiles
Failure to Choose Effective Proxies
Failure to Rebuild
Securing the Borders
The Rhetoric and the Reality of Democracy
The Failure of Justice
Militias: The State Monopoly on Force
Israeli Occupation Tactics
The Sparks: Mishandling al-Sadr and the Fallujah Atrocity
In other words, FUBAR...