There are a few reasons to explain why the United States has never intervened to prevent genocide. In the years leading up to World War II, the United States was dealing with the effects of the Great Depression. Our attention was focused on trying to deal with the worst economic crisis in our history. As a result, our focus was more on events at home than on events abroad. Additionally, there was some backlash from World War I. There were reports, suggested by the study of the Nye Committee, that we joined World War I so our businesses could make money. People were very hesitant about getting involved in world affairs, in part because of the concerns expressed in this report.
Another factor that may explain our lack of involvement is the American people have been hesitant to get involved in situations that don’t directly affect us. We have been hesitant to do this because it could lead to a long and a costly involvement in trying to stop the killing that was occurring. We have seen fairly recent examples of this with the wars in Afghanistan and Iraq. It also was true to some extent with the Vietnam War. The American people are hesitant to get drawn into a situation that could lead to years of involvement trying to resolve a situation that may appear to our people as an unresolvable situation.