International relations between United States and Europe exist since 19th century. The United States are the most important center of power in the modern world, with the largest economic, military, political and cultural power in the world. Europe is also an important factor in international relations, and in the modern political order, Europe is the most important strategic partner of the United States. International relations between United States and Europe in creating contemporary world politics can be seen from the beginning of the First World War. Two major wars were crucial for shaping the world order, whose frontiers were determining by United States and Europe as two most important actors in the world. Importance of the European Union as a political community of European nations, is the result if its economic power. Although Europe and the US are partners in international politics, the dominance of the United States was specially seen after World War II. With the appereance of Cold War, relations between the US and Europe, but also those in the international scene have significantly changed. The base of the relationship between United States and Europe is the North Atlantic Treaty Organization, which is today one of the most important political and military alliance. The Cold War was the most dynamic period in the relations between the US and Europe, after which American-European relations had begun refer on the relations between the United States and Russia. The beginning of the 21st century has brought new challenges to global and national security. After the Cold War United States get third time the opportunity to create a new world order in which the most important are relations between the United States and Russia, as the backbone of future geo-strategic initiatives around the world.