One reason the Untied States maintains its possessions is because it is a good deal for them. They get far more in aid from Washington than they send the other way. Puerto Ricans, for example, do not pay federal income taxes but are still eligible for federal welfare benefits, such as food stamps.

This illustrates an important point about colonialism that France and Britain also discovered -- it just doesn't pay. Even admirers of the British Empire, such as economic historian Niall Ferguson, admit this fact. In his recent book, "Empire" (Basic Books), he notes that Britain put far more into India in the form of public works and military expenses than it ever took out. In "Mammon and the Pursuit of Empire" (Cambridge University Press), economic historians Lance Davis and Robert Huttenback concluded that Britain lost money on all its colonies. That's why they were ultimately given their independence.

Iraq is further evidence that colonies are a losing proposition. Even though that nation sits on the second largest proven oil reserves on earth, production is coming back on line very slowly. This is forcing U.S. taxpayers to pay for the reconstruction of Iraq on top of the large and growing costs of occupation. And, of course, the biggest cost is unquantifiable -- the 261 American military personnel who have lost their lives in the Iraq conflict.

When asked, President Bush and his advisers disavow any imperial ambitions. "We have no territorial ambitions, we don't seek an empire," President Bush has said. But as journalist Robert Merry writes in the latest issue of International Economy Magazine, "History tells us that empires of the past seldom set out to become empires."

I don't believe that anyone in the Bush administration consciously desires an American empire, although they are being urged to pursue one by pundits like William Kristol. But I do think there is a danger that the United States will back into imperialism if we aren't careful. All the old reasons against it are still valid and should be respected.