I found this article by Victor Davis Hanson entitled "A Funny Sort of Empire" quite interesting.

Athenians, Romans, Ottomans, and the British wanted land and treasure and grabbed all they could get when they could. The United States hasn't annexed anyone's soil since the Spanish-American War — a checkered period in American history that still makes us, not them, out as villains in our own history books. Most Americans are far more interested in carving up the Nevada desert for monster homes than in getting their hands on Karachi or the Amazon basin. Puerto Ricans are free to vote themselves independence anytime they wish.

...and in conclusion:

Much, then, of what we read about the evil of American imperialism is written by post-heroic and bored elites, intellectuals, and coffeehouse hacks, whose freedom and security are a given, but whose rarified tastes are apparently unshared and endangered. In contrast, the poorer want freedom and material things first — and cynicism, skepticism, irony, and nihilism second. So we should not listen to what a few say, but rather look at what many do.

Critiques of the United States based on class, race, nationality, or taste have all failed to explicate, much less stop, the American cultural juggernaut. Forecasts of bankrupting defense expenditures and imperial overstretch are the stuff of the faculty lounge. Neither Freud nor Marx is of much help. And real knowledge of past empires that might allow judicious analogies is beyond the grasp of popular pundits.

Add that all up, and our exasperated critics are left with the same old empty jargon of legions and gunboats.

I agree with most of what Hanson says. He does a fine job of pointing out the ridiculousness of assertions that America today is in any way "imperialistic", at least in ways analogous to empires of the past.