America wanted to become an imperial power because the European nations split up Africa for its resources which left the United States behind.
Also, the European nations used spheres of influence in China in order control sections of the country for natural resources and trade so the United States created the Open Door Notes which allowed all nations to trade with China.
Third and final reason, the U.S. wanted overseas territories in order to refuel their navy which had to be powerful, as argued by Alfred T. Mahan, they also colonized nations in order to draw out their natural resources, most importantly sugar. Finally, the U.S. wanted to influence small Pacific island nations so the U.S. can build defensive outpost to protect the U.S. mainland.
