To what extent did the United Sates act as a traditional imperial power between 1900 and 1920?

The United States intervened heavily in the lands it acquired during the Spanish-American War. It fought a war against Emilio Aguinaldo in the Philippines when it looked as though he would gain control of the country. The United States also gave itself considerable power in Cuba, maintaining the right to intervene at any time and keeping Guantanamo as a naval base. The United States also intervened all over the Latin world, sending troops to Haiti and Mexico in order to support governments friendly to American interests.
Militarily, the United States sent the Great White Fleet on a worldwide cruise in order to demonstrate American naval might and to attempt to intimidate the Japanese from expanding into areas where the United States may have an interest. A group of American marines were sent to suppress the Boxer Rebellion, and the United States authored the Open Door policy in China, which took away the concept of spheres of influence.
Diplomatically, the United States was a major contributor in ending World War I, though many of Wilson's altruistic goals were lost at the Versailles conference. The United States also helped broker a peace between Russia and Japan in 1905, earning Theodore Roosevelt a Nobel Peace prize.