Which nation emerged as a leading world power after world war 1

The United States emerged as a leading world power after World War I due to the Treaty of Versailles.

The United States of America emerged as the leading world power after the events of World War I. Aside from the Treaty of Versailles (which was one of the reason why the United States became a superpower), Unites States' economy increased due to the US' government heavily investing in the war by lending money to the Allied Powers.