No, it is false that Imperialism was the name given to the idea that Americans should expand across the nation to the Pacific Coast, since what you're referring to was known as "Manifest Destiny".
I believe it's C. Zhu Yuanzhang hope it's right :)

Type that in your calculator to get 268, hope that helped
Monroe Doctrine is the best known U.S. policy toward the Western Hemisphere. Buried in a routine annual message delivered to Congress by President James Monroe in December 1823, the doctrine warns European nations that the United States would not tolerate further colonization or puppet monarchs.