The closest parallel to terrorism that we have in the scriptures is the Gaddianton robbers. The Nephits ultimately defeated the robbers not by going up against them (the way the U.S. has tried in Iraq) but by gathering all their armies together in the center of the lands, drawing them out.
If the U.S. would withdraw from Iraq, the terrorists would be exposed like rocks in a dry lakebed, and the local people would deal with them.