Manifest destiny advanced the belief that

God was on the side of American expansion, is the right answer.

Explanation:

Coined in the year 1845, Manifest Destiny was a phrase that gave the idea that God has destined the U.S. Accordingly the supporters of this idea, believed that God was on the side of American expansion and thus they had the divine authority to expand the territory of the United States and spread capitalism and democracy beyond the entire North American continent.

During the 19th century, this philosophy not only inspired territorial expansion of the United States but also justified the forced removal of Native Americans and other groups from their homes.