Iraq’s leaders have a tentative constitution, but they've postponed a fundamental question--can Iraq really exist as one nation?

The Kurds and Shiites negotiated the draft charter, the Sunnis are left to take it or leave it, and the whole affair has literally papered over deep divisions about regional autonomy, oil revenues, Islamic law and more.

By demanding one new Iraqi state, the U.S. and its allies are ignoring the lessons of recent history. They are spending blood and treasure to preserve a country that no longer makes sense as a state, and to keep together people who only want to be separate. Iraqis might get closer to democracy, and the U.S. might get closer to its goals in the Middle East, if everyone would jettison the fiction of a unified, single Iraq.

There has never been serious consideration given to the idea of dividing Iraq in a way that would align with its distinct ethnic and religious groups. The Bush administration declared that it would remove Saddam Hussein and install a democratic government and that Iraq's borders would remain intact. In April 2003, President Bush told the Iraqi people, "Iraq will go forward as a unified, independent and sovereign nation that has regained a respected place in the world."

That desire lines up with American foreign policy since the close of the Cold War. In the early 1990s, the U.S. resisted the collapse of the Soviet Union into separate republics. We are still trying to hold Afghanistan together as one country. The U.S. has intervened in such places as Somalia and Haiti to rebuild states--with spectacular lack of success--that cannot control conduct within their borders. The former Yugoslavia, where NATO appears to be encouraging fragmentation, has proved to be the only significant exception to the policy rule. For the United States, it seems, it's either the original nation-state or nothing.

Meanwhile, a great wave of decentralization has occurred throughout the world. In 1945, for instance, there were 74 independent nations; today, there are 193 (two more if you count Taiwan and a nascent Palestinian state). And with decentralization has come economic growth, and more democracy. Even the seemingly centralized European Union acts to break down traditional nation-states into smaller regions that cooperate in varying trading groups across old borders.

Large, diverse nations make sense when they can efficiently provide "public goods" such as defense and law and order. But such nations are also costly and difficult to maintain, because--as we see in Iraq--it isn't easy to force people with very different values, needs and desires together.

Economists say that as the threat of wars among nations recedes and free trade agreements expand, nation-states will become smaller naturally. People will trade in the protection offered by large states for the interconnections of globalism. In fact, by supplying security and supporting free trade over the last half-century, the United States has been encouraging the very fragmentation it is fighting in Iraq.

Dividing Iraq into three parts would take advantage of these trends. Allowing the Kurds, Shiites and Sunnis to operate independent states would reduce divisions over the design and power of their governments and speed the reconstruction of state institutions. It would allow each group to find consensus on questions of religion and law and concentrate its strength within compact, defendable borders that follow natural geographic and population boundaries. It would undermine the insurgents' cause and their ability to carry out attacks. And that would enable U.S. and coalition forces to withdraw.

The difficulties that have plagued the creation of an Iraqi constitution signal that the United States should reconsider the heavy costs of maintaining states such as Iraq. It isn't a given that the borders of Iraq should remain permanent or that the United States and its allies should waste time, lives and money to force together groups that are willing to kill each other.

Americans have faith that a constitution, virtually by itself, can weld together disparate peoples and places. But the United States became a nation not only through the Constitution but also through the fiery experience of the Civil War. Only then could Abraham Lincoln reconstruct "the United States" into a singular, not a plural, noun.

We should not forget how unique our experience is. Most European and Asian countries were nations--with a dominant language, religion and values--before they became states. In Iraq, we're working the equation backward. Its unhappy factions show that it is not a nation. Its troubled constitutional process shows it may never be a unified state.

John Yoo is a visiting scholar at AEI.