[Fuzz]

“It was being “renegotiated” to leave a sustaining force for the transition. There was no serious effort to complete this, however.”

One of the biggest reasons, as I recall, was because Iraq would not agree to immune our troops from prosecution and the fact that they wanted us out.

[Alberta's Child]

Which means that the U.S. government withdrew military forces from Iraq for the same reason it's withdrawn military forces from foreign countries all over the world for more than two centuries.

You simply can't have U.S. military forces subject to foreign legal systems like that -- especially in a place like the Middle East where most governments are run by baboons.