As usual, Virginia Postrel says it better than I ever could:
It's common on the left and even more common among isolationist libertarians to charge that the United States is, or is becoming, an "empire" because of interventions abroad. Hearing it the other day, I was struck by how utterly absurd the term is. If this is an empire, where's the emperor? Where's the territorial control? Where's the tribute flowing from overseas possessions? Saying the word empire is the wrong one doesn't imply that U.S. foreign policy is correct, merely that another term is needed. A 21st-century representative democracy with a large regulatory bureaucracy and many overseas involvements may be problematic. But it isn't an "empire" unless that term just means "a government I don't like."
As for the nonstop blather -- particularly popular among antiwar types -- about the "failure of diplomacy"? About the only failure I can detect may be a miscalculation by the U.S., U.K., et al., that they were negotiating with serious, responsible adults -- and I'm not talking about the Iraqis. Clearly, the French, Germans and Russians have no intention of countenancing military force against Saddam under any circumstances ... unless, say, a team of U.N. inspectors had unearthed a cache of 30 nuclear-tipped warheads or a factory producing VX gas round the clock. The question reporters should be posing to diplomats ought to be targeted to those opposing military action at this point: "If you are incapable of setting any deadline for Iraqi compliance with United Nations resolutions, why did you support Resolution 1441 in the first place?"
I truly hope reports that Saddam is equipping his forces with chemical and bio weapons are wrong. If not, I'll not be surprised if the plumbing fixtures from U.N. Headquarters are for sale on eBay before summer.