I am not quite sure, but i believe that US interference has been conducted since WWII. the main purposes were to indirectly occupy natural resources in other countries, for instance, Saudi Arabia has been protected by USA since WWII and to prevent other power countries to spread thier territories, for instance, USA sent troops in Afghanistan to prevent and push USSR army out during the cold war. After the cold war, none major power countries dared to fight against USA. Therefore; it was a time for USA to spread its economic, military and political influnces. You can see how USA devides the world and how many international military bases are on earth form the pentagon web site. After the cold war, USA became the sole super power instead of Britain, frence, and german. In twentith first century, there are several emerging major countries, such as China, Russia, India,and European countries. in this era, US intervention is about global enery security, no more for political ideology.