Would it be out of the question to have, say, Blackwater units?
Mercenaries are the second largest force in Iraq now, at an enormous expense. Aparently, they pay so much better than the regular armed forces, that our highly trained people get jobs with them instead of re-enlisting. Kind of a force vaccuum.
They would mostly have the same gear as the US, but they would have to simulate armored SUV's and lots of guys with slick sunglasses. And looser rules of engagement.
http://www.blackwaterusa.com/about/
http://news.scotsman.com/opinion.cfm?id=1013202004
And then there are the Force Ministries guys. I wonder why Muslims could percieve the Iraq War as a crusade? Oh, maybe its these bullets for Jesus guys "imparting faith in Christ" while holding an M-16. Nice.
http://www.forceministries.com/whoweare.html
Its entirely possible, in fact likely, that if US action against Syria was taken, PMCs would either be in left in nearly full 'control' of Iraq, or part of supplementry security operations during an invasion.