What is the best summary of the first paragraph of "How We Entered World War I"? The United States was not considered a great power until it entered World War I, thus beginning its continual involvement in world affairs. The Spanish-American War gave the United States a basis of power so it could enter World War I as a great power. The United States entered World War I as a great power but has not influenced world affairs in the same way since. The United States has always been considered a great power, despite its desire to withdraw from world affairs.