During this time the idea of expanding the U.S. on a global level became one of Americas prime goals. Many people were involved in this process not just for economic reasons but for religion as well. Protestants were among the religous groups most known for doing so as there were also imperialists and business men involved in this exanpansion as well.
President Roosevelt was the main iniator of this process as he felt that in order to become a more prosperous nation we must conquer and control new territories and resources to become a global power. Not only did we establish better relations with other countries at this time but we made trade easier by creating the panama canal which allowed for more efficient transportation of goods from one part of the U.S. to the other.
It was also during this time that WWI broke out in which the U.S. really gained power from as they emerged as the new global leader. No longer was the the world multipolar but rather bipolar as the U.S. and Russia became the new global powers.