Final answer:
The United Nations (UN) is the international peacekeeping organization created to prevent future world wars. The UN replaced the League of Nations and consists of member nations represented in the General Assembly and a Security Council. The United States played a leading role in supporting and joining the UN. Another important organization to prevent wars is NATO.
Step-by-step explanation:
The international peacekeeping organization that was created to prevent future world wars is the United Nations (UN). The UN was established after World War II with the goal of ensuring international peace and stability. It replaced the ineffective League of Nations that was created after World War I.
The United States, despite rejecting the League of Nations, played a leading role in supporting and joining the UN. The UN consists of various member nations represented in the General Assembly and a Security Council composed of permanent members, including the United States, Soviet Union (now Russia), France, Britain, and China, who have veto power over proposed policies.
Another cross-national organization that the United States is tied to is the North Atlantic Treaty Organization (NATO). NATO was formed after World War II to protect the interests of Europe and the West and to ensure peace and stability. Although more militaristic than the UN, NATO's main goal is not expansion but rather the assurance of support and defense from partner nations.