The US is the most powerful single force in Iraq but it is by no means the only one. The shape of Iraqi politics have changed over the last year though for reasons that have little to do with 'the Surge'--the 30,000 US troop reinforcements -- and much to do with the battle for supremacy between the Sunni and Shia communities.
The Sunni Arabs of Iraq turned against al Qa'ida partly because it tried to monopolize power but primarily because it had brought their community close to catastrophe. The Sunni war against the US occupation had gone surprisingly well for them since it began in 2003. It was a second war, the one against the Shia majority led by al-Qa'ida, which the Sunni were losing with disastrous results for themselves.
"The Sunni people now think they cannot fight two wars--against the occupation and the government--at the same time," a Sunni friend in Baghdad told me last week. "We must be more realistic and accept the occupation for the moment."