In fact, our military presence in Iraq will be modified due to domestic public opinion.
There's another major military intervention coming up pretty damn soon, if you've been following the news. And we've had all sorts of lower-level military action going on in areas outside of Afghanistan and Iraq, most especially in the tribal areas of Pakistan.
If our military stance in Iraq is modified by domestic opinion rather than military considerations, then that is a victory for our enemies and domestic opposition alike. I hope that is not something you are counting on.