The article raises the problem of American imperialism. The author proposes a new approach to the issue. He states research should concentrate on understanding, taking into consideration mental, intellectual and emotional aspects. As an example, the author provides an analysis of argumentation of proimperial elite of United States from the turn of 19th and 20th century. As a background of that analysis, drawing on methodological approach of Ferdynand Braudel, the author also provides an outline of imperialism in the United States. Likewise, he points at psychological mechanism of cognitive dissonance as important factor in forming the argumentation. The author notes it was focusing on proving imperialism to be moral. He identifies main areas of argumentation: (1) identification imperialism with the expand of an American model of political system, which was considered to be ideal; (2) bringing civilization to the uncivilized nations; (3) presenting imperialism as a mission from God; (4) referring to the law of nature; (5) justifying expansion with the safety issue; (6) referring to the idea of New Manifest Destiny.