What is the name given to the belief that the US have the right and duty to expand across North America continent?

The belief that the U.S. had the right and duty to expand across the North American continent is known as "Manifest Destiny." This concept emerged in the 19th century and was used to justify territorial expansion, including the annexation of territories such as Texas and the acquisition of lands from Mexico. It was rooted in a sense of American exceptionalism and the belief that it was the nation's destiny to spread democracy and civilization.