Often things look totally different on the way out than on the way in. Like any other government effort, there were some that approved and some that didn't. Congress approved the invasion, a vote that many of them would rather forget.
I don't think the war was in the interest of the U.S. or Great Britan in any way. If the Iraqi people can hold their new government together, they will benefit. I believe history will see the Iraq war as the point when the world learned the UN was a tiger with no teeth; the time when international relations became, "everybody for himself" rather than any joint effort to make the world a safer place to live. If you look at what's going on in Africa, North Korea and Iran today, they are living testimony to the effect of the Iraq war.