What reasons allowed the United States to become the new leader of Western civilization

What reasons allowed the United States to become the new leader of Western civilization at the turn of the 19th and 20th centuries?

Probably the most important reason can be called the First World War. The fact is that, although the United States took part in the war, no hostilities took place on its territory. This made it possible to develop the economy more actively after the war, while other countries were just beginning to rebuild their own after the war. Also, during the war, the United States issued dollars that were not backed by gold, which made it possible to issue loans to Western European countries. Also, the competent policy of the US government had a great influence.