While ideology was important as Americans wanted to spread their culture, economics were the driving factor in American foreign policy at this time. The United States overthrew the rightful queen of Hawaii so that American pineapple and sugar growers on the island could avoid paying tariffs. The United States went to war with Spain only to protect American interests in Cuba. Spanish atrocities were given as the reason for the invasion; if this were the only reason, then the United States would not have annexed the Philippines and Guam in that same war. The United States annexed the Philippines and Guam and bought Wake Island and Samoa in order to establish coaling stations in order to reach the lucrative Asian markets needed for American industrialists.
Even when the United States did not annex new territory, it created spheres of influence through diplomacy and military intervention. The United States brokered the Open Door policy in China not out of love for Chinese independence; rather, it was to ensure that the US had a place at the table for trade in China. The United States intervened heavily in Mexico's revolutions before WWI to protect American oil interests in the region. An argument can also be made that the US's decision to enter WWI was done in order to protect American loans to the Allies and to protect American shipping interests.
American foreign policy during this period often claimed to be dependent on human rights and protecting freedoms, but underneath these humanitarian aims lay a strong undercurrent of protecting American economic interests.