Suddenly, It's 'America Who?'
Dexter Filkins article holds that Jan 30 elections altered Iraq's relationship with US more than any single event since invasion; maintains that since Saddam Hussein's rule crumbled, Iraqis have viewed themselves as American subjects; says that changed when millions of Iraqis streamed to polls; contends that few Iraqis had ever voted in free election, yet most seemed to know exactly what exercise was about: selecting their own representatives to lead their own country; photo (M)