Westward Expansion Via Manifest Destiny LG: How did Americans come to believe in Manifest Destiny? Americans came to believe in Manifest Destiny, by John O’ Sullivan stating, “God has given land to Americans”. Thus, making the country to believe that it was justifiable, that Americans should expand the country from coast to coast. Though the expansion lead to Sectionalism with the North and South. Due to America’s history, culture, and government, Americans thought that they were the best…