Why indeed?
Charles Krauthammer in the Washington Post says to President Bush, Don't Go Back to the U.N.:

No one knows when this war will end. But when it does, you'll have to decide the terms. Yet in the past few days both you and Tony Blair have said you will seek a new U.N. resolution, postwar, providing for the governance of Iraq.

Why in God's name would we want to re-empower the French in deciding the postwar settlement? Why would we want to grant them influence over the terms, the powers, the duration of an occupation bought at the price of American and British blood? France, Germany and Russia did everything they could to sabotage your policy before the war. Will they want to see it succeed after the war?

The Frankfurter Allgemeine reports that on Feb. 21, Germany's U.N. ambassador, Gunter Pleuger, wrote his Foreign Ministry that the United States, blocked on a U.N. war resolution and fighting alone, would later "remorsefully return to the council" to seek help in rebuilding Iraq.
...
You've seen the polls: Seventy-five percent of Americans disapprove of how the United Nations handled the situation with Iraq. In December, polls showed a majority of Americans opposed to a war without U.N. backing. Today, after the U.N. debacle, 71 percent support the war regardless.

What happened? Americans finally had a look inside the sausage factory. Their image of the United Nations as a legitimating institution had always been deeply sentimental, based on the United Nations of their youth -- UNICEF, refugee help, earthquake assistance. A global Mother Teresa. That's what they thought of the United Nations, and that's why they held it in esteem and cared about what it said. Now they know that it is not UNICEF collection boxes but a committee of cynical, resentful, ex-imperial powers such as France and Russia serving their own national interests -- and delighting in frustrating America's -- without the slightest reference to the moral issues at stake. The American public understands that this is not a body with which to entrust American values or American security.

Mr. Krauthammer provides a refined assessment. I'm just an old country boy and prefer the sentiment in this oft linked picture: