The correct answer to this open question is the following.
The important American beliefs and values that were involved in the westward movement was the idea of Manifested Destiny supported by US President James Polk. Polk believed that the US was superior to Mexico and it had the divine right to conquer and expand. Polk considered that Americans were a superior race with the right to expand their territory. And expand they did. This shaped the westward experience and the westward movement entangled the United States in the affairs of foreign powers such as the Mexican-American War in which after victory and through the signing of the Treaty Guadalupe-Hidalgo, the United States acquired the territories of Califonia, New Mexico, Arizona, Utah, and Nevada.
