Many wars that have involved the United States do typically revolve or are concerned with the type of government in the country. Communist governments have taken part in many wars. Since the United States was opposed to communist governments, they would often fight wars against countries that had these governments. In addition to that, these governments were believed to have dictators that were cruel to their people.
When this would happen, the U.S. wanted to help the citizens of the country who were being tormented by their government, so they took action. This would usually result in a war breaking out. Most countries would not need to worry unless their governments are committing genocide where they are trying to kill an entire race in the country.