Our forces, although been handicapped and slow, building the Iraq forces to do the job. Building an Army from scratch is not easy and takes lots of time. And much of the control of the extremist is being cleaned up by the Iraqi forces which are doing a great job. Sure there will be terrorist attacks and may even be increasing, but "criminals" do not obey the law, neither here in the US or Iraq.
It would have been easier and taken less time if we had not gone in for Limited war in the first place. See Japan.