The United States Completed Manifest Destiny At The Cost Of The Mexican The Mexican-American war lasted two years, and ended with the signing of the Treaty of Guadeloupe on February 2 1848. The United States had succeeded in winning the war. With the Treaty of Guadeloupe the United States had succeeded in completing its Manifest Destiny. The Treaty itself represented the United States expansion goals. The United States wanted to settle on were the international border was to be. Mexico wanted the border to north of the Rio Grande river, but fi ....