Manifest Destiny was the idea that the U.S. had a god-given right and duty to expand coast to coast. This idea was propagated through newspapers and nationalist politicians. The idea of Manifest Destiny reflects Nationalism and the belief that American institutions and ideas (ex: Democracy, Republicanism, Protestantism) should be spread, and the racist idea that Anglo-American ways of being (culture) are superior to Native American or Mexican ways of being.
Manifest Destiny | Summary, Examples, Westward Expansion, & Significance |  Britannica