Imperialism: The policy of extending a nation's power and influence through economic, political, or military means. It was an ongoing trend during both World War I and Vietnam War as major powers sought to expand their territories.
Containment: A U.S. foreign policy strategy during the Cold War aimed at preventing the spread of communism by containing its influence within its existing borders.
Globalization: The increasing interconnectedness of nations through trade, communication, and cultural exchange. It has been an ongoing trend in American foreign policy as technology advances and economies become more integrated.