Americans believed expansion would offer new economic opportunities. this perception is known as

Americans believed expansion would offer new economic opportunities. This perception is known as Manifest Destiny.

Explanation:

Manifest Destiny was a 19th-century American belief that the United States was destined to expand across the North American continent.

The term was first coined by journalist John O'Sullivan in an anonymous article published in 1845 by The United States Magazine and Democratic Review, in which he defended the fate of "allowing" the United States to expand across the continent and allow a growing nation to develop freely.  

During the Mexican-American War and later, the term was used to justify the annexation of the western territories of Mexico (Arizona, Texas, California, etc). On the eve of the Spanish-American War, the term was revived by the Republicans to give a theoretical justification for the US foreign expansion.

The term has ceased to be widely used in politics since the beginning of the 20th century, but in journalistic literature it continues to be widely used to refer to the American "mission" to promote democracy throughout the world. Understood in this sense, the “explicit purpose” of American statehood continued to influence the ideology of the ruling circles of the United States in the 20th century.

map scale refers to the relationship (or ratio) between distance on a map and the corresponding distance on the ground. for example, on a 1: 100000 scale map, 1cm on the map equals 1km on the ground.