The three correct statements that describe the Spanish-American War and the resulting debate over American Imperialism are:
B. One argument against American imperialism was that it would be costly to maintain territory outside American borders.
C. Social Darwinism was the concept that the United States and Western powers were better suited to govern other parts of the world and would bring civilization.
E. Increasing trade and opening up new markets was a major argument in favor of American imperialism.
Statement A is incorrect because Theodore Roosevelt did not found the Anti-Imperialistic League; in fact, he was a proponent of imperialism. Statement D is also incorrect as Hawaii became a U.S. territory through a coup and annexation, not a purchase from Russia.