What does Albert Gallatin think is the real motive underlying the idea of Manifest Destiny?

Albert Gallatin thinks the real motive underlying the idea of Manifest Destiny is the following one:

US thinks we are superior

Manifest Destiny was the belief that America should expand all over the North American continent as it was their divine destiny to remove Native Americans and other nations from their continent. Gallatin believed that this was only to show everyone the supremacy of the American nation.