Why did the u. s. change from isolationism to a policy of imperialism during the late 19th century?

The reason for the change from isolationism to imperialism was because America was slowly becoming a superpower in the world during the 19th century. This was also due to the fact that America felt that it could maintain "peace" in the world through its power. To hold its status as a superpower, America had to take steps to establish itself around the world. The Imperial rule allowed it to compete with European states in terms of resources and money.