Answer:
Manifest destiny
Step-by-step explanation:
In 1853, the Mexican government kicked Americans out of the territory. ... Congress ratified a revised version of the treaty; the U.S. would purchase just over 29 thousand square miles of land in exchange for $10 million. The Gadsden Purchase secured area for the transcontinental railroad and set the U.S.-Mexican border.
Manifest Destiny, a phrase coined in 1845, is the idea that the United States is destined—by God, its advocates believed—to expand its dominion and spread democracy and capitalism across the entire North American continent.
There are three basic themes to manifest destiny: The special virtues of the American people and their institutions. The mission of the United States to redeem and remake the west in the image of agrarian America. An irresistible destiny to accomplish this essential duty.