When they speak of the American empire, critics fall back on cartoonish notions, invoking Hollywoodized versions of ancient Rome or mothballed Marxist caricatures of the British Raj. But unlike the Romans, or even the British, our garrisons can be ejected without firing a shot. We left the Philippines when asked. We may split from South Korea in the next few years under similar circumstances. Poland wants our military bases; Germany is grumpy about losing them. When Turkey, a U.S. ally and member of NATO, refused to let us invade Iraq from its territory, the U.S. government said "fine." We didn't invade Iraq for oil (all we needed to do to buy it was lift the embargo), and we've made it clear that we'll leave Iraq if the Iraqis ask.

The second verse of the anti-imperial lament, sung in unison by liberals and libertarians, goes like this: Expansion of the military-industrial complex leads to contraction of freedom at home. But historically, this is a hard sell. Women got the vote largely thanks to World War I. President Truman, that consummate Cold Warrior, integrated the Army, and the civil rights movement escalated its successes even as we escalated the Cold War and our presence in Vietnam. President Reagan built up the military even as he liberalized the economy.

Sure, Naomi Wolfe, Frank Rich and other leftists believe that the imperialistic war on terror has turned America into a police state. But if they were right, they wouldn't be allowed to say that.

Two compelling new books help explain why our "empire" is different from the Soviet or Roman varieties. Walter Russell Mead's encyclopedic "God and Gold" argues that Anglo-American culture is uniquely well suited toward globalism, military success, capitalism and liberty. Amy Chua's brilliant "Day of Empire" confirms why: Successful "hyperpowers" tend to be more tolerant and inclusive than their competitors. Despite its flaws, Britain was the first truly liberal empire.

America has picked up where the British left off. Whatever sway the U.S. holds over far-flung reaches of the globe is derived from the fact that we have been, and hopefully shall continue to be, the leader of the free world, offering help and guidance, peace and prosperity, where and when we can, as best we can, and asking little in return. If that makes us an empire, so be it. But I think "leader of the free world" is the only label we'll ever need or - one hopes - ever want.