Imperialism. From Dictionary.com the definition is: the policy of extending the rule or authority of an empire or nation over foreign countries, or of acquiring and holding colonies and dependencies.
Now let's ask something here. Are we in fact, practicing Imperialism? Did the Global War on Terror, and its two main theaters in Iraq or Afghanistan create a colony, or "dependency"? Last time I checked we spent over a trillion Dollars so they wouldn't have to call on us for every little thing (to include radicals). Indeed despite "War for Oil" claims at oh so many protests, I have yet to see any evidence of actual you know war for oil. Oil was seen as a tool for economic recovery, and was thus vital to the Iraqi people, not the American. Had OIF been about Oil, well really how hard would it have been to station 150,000 troops around the oil fields and pipelines? We could have let the country fall into chaos while happily driving down the cost of Gas to $.50 and telling OPEC to kiss our ass.
How about Afghanistan. Are there any resources there worth plundering? Their women look like hell (probably because they've been treated that way) outside of the cities, you are almost traveling back in time, and in the tribal regions, one might as well be living 1000 years in the past. While one might argue that there is some great hiking, and picturesque views, we're not exactly trying to ship Outward bound to A-stan. What resources are there for us that we couldn't get anywhere else for cheaper?
Going back to the late 60's and early 70's there has been a charge of Imperialism by the Liberal Left. This charge, strangely would have actually had merit in the progressive era (the forerunner to the modern Liberal era of the Left), when Progressive Presidents, did in fact try to colonize the world. To understand this you'd have to understand that post Spanish American War, we were suddenly sitting on the Spanish colonies of the Philippians, Cuba, Guam, and a couple of other notable islands. Suddenly the burgeoning America had access to. . . well the entire Western (and parts of the Eastern) Hemisphere and most of the Imperial European powers couldn't say a thing about it.
What did we do? Turned right around and gave it back to them (this is of course after the Progressives left power). To my Knowledge, there are only 50 states. Even the Territories get privileges that Colonies do not (most of the time the support going from America to the Territories not vice versa. Ask yourself this, "what have we gained from the wars we have fought?" This Question is actually something that ironically enough is used by the same people who make the charge of Imperialism, as a barb against further wars, this is much like having their cake and eating it too, and it is a shame that more people do not call them out on this logical inconstancy.
So let's ask this question which is far more important: "Why do we fight?" The majority of the Wars that America has fought in are in response to aggression, the sole exceptions I can find would be OIF (the one example I can find of "preemptive war"), and the Indian Wars (but, even there, it was in response to perceived aggression). The Spanish American War the only war I could possibly see to support the charge of Imperialism (more for its aftermath than its beginning) Began because of Concentration Camps (yes it was in fact the Spanish, not the Germans that started that particular tradition), and abuses of the people. WWI, WWII, Korea even Vietnam, all in response to aggression, and despite a few extreme examples, there were no abuses by Americans that ever matched our enemies. Even in Iraq and Afghanistan there have been only a handful of convictions, and even those were questionable, and yet the abuses of our enemies are extremely well documented, if not reported.
Further the only time that there really was "Imperial" power in the presidency, during the Cold War from about 1946-1965, one would be hard pressed to argue that everyone under the protection of America, did not benefit (and greatly at that) from that protection. Can Japan, or Germany, France, or the Pacific, truly argue that we abused them as they would have to their colonies?
So then I would suggest this, America goes to war, not for profit or gain, as Empires do. Not even for the "Glory" of our nation do we go to war. Yes that may be the reason for an individuals to go, but not for us as a nation. We are unique in that after defeating our enemies we do not demand tribute. We are unique in that we do not demand payment for the wars. We are unique in all of human history, in that we fight for a non-concrete ideal. Because we have a deep and firm belief, that every person, every human being should have the opportunity, even the joys we enjoy. We can not point to any one thing that we have done to improve the world, only that the world has improved, more and more because of our influence not despite it. In Iraq, we sought to raise and create, our enemies sought to destroy. Now we have left them with the right to determine their own fates. Is this the work of Ceasers Czars, Kaisers, Emperors, or Empires?