I think the administration has to make noises about the Shia and the Iranians in order to appear fair, but the fact remains that the vast majority of US casualties are the result of Sunni Arabs.
Which leads to the question about where THEY get their money, arms, etc...
Sunni Arabs like this from PBS from early 2002.
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The U.S. says Al Qaeda fugitives may have slipped into Iran, and that some may have found sanctuary there, including Abu Musaab Zarqawi. The New York Times reported on March 24 that Zarqawi, "a senior Al Qaeda leader who fled the western Afghan city of Herat after the American military campaign began, has turned up in Tehran under the protection of Iranian security forces, according to senior Israeli and American officials." Defense Secretary Donald Rumsfeld said on ABC's This Week in early February, "We have any number of reports that Iran has been permissive and allowed transit through their country of Al Qaeda." Iran denies that it has provided any assistance to Al Qaeda fugitives.
http://www.pbs.org/wgbh/pages/frontline/shows/tehran/axis/map.html