In the late 1800s and early 1900s (up through World War I) there were two main competing ideologies that informed American foreign policy. Generally speaking, these were the policies of idealism and of imperialism.
This period saw the beginning of American overseas imperialism. There were many people, such as Theodore Roosevelt and Alfred Thayer Mahan, who wanted the US to exert power around the globe. They wanted the US to be a major power in the world, and this meant having something of an empire. This inspired such things as the taking of the Philippines after the Spanish-American War and the frequent interventions in Latin America under the Roosevelt Corollary to the Monroe Doctrine. This ideology held that US foreign policy should work to advance American interests rather than American values.
On the other hand, there were people who felt that it was important for American foreign policy to exhibit American values. This group felt that imperialism was immoral. Mark Twain was one such person. He opposed fighting the Filipinos on the grounds that they were people who were trying to gain independence and Americans ought to support people who are fighting for such a cause. President Woodrow Wilson tried to act idealistically as well. He tried, for example, to make WWI be a war that would bring about a new and peaceful world order.
These are the two main competing ideologies seen in American foreign policy in the late 1800s and early 1900s.