What is Evil?

What does evil mean? Labeling an act evil is a dangerous thing. Peoples perception's of good and evil are different all over the world. The majority of Americans saw 9-11 as a "evil" act but there are entire countries that would disagree with us. People say murdering a child is evil but the same people might think that abortion is ok. Many, if not all, people would say that Hitler was evil but had Germany won the war all of our perceptions would change. It seems that in America we as a country need a "evil" enemy to justify our military and our imperialistic actions. We first called England "evil" during the revolutionary war and then the Axis countries in WW I and II. Then communism and now Muslim extremists and terrorists. Evil is a subjective term and used as a blanket to cover up all kinds of American wrongs. Think about that? I am not saying that only America acts that way worldwide all countries seem to have a flexible grasp on "evil" depending on what they are trying to accomplish. Perhaps I shouldn't say countries but empires. Because (and make no mistake here) America is an empire it is just up to us wether or not we become an "evil" one or not.