How did westward expansion change the world?
American westward expansion changed the world in several ways. Of course, it permanently altered the lives of the millions of Native Americans who lived in the West, but it also had major geopolitical implications. For example, the expansionist ambitions of the American colonies were a major cause of the French and Indian War, which in turn gave rise to the Seven Years' War, a massive conflict with major implications. The importance of the port city of New Orleans to westward expansion played a major role in diplomatic maneuvering between the United States, Spain, and France in the period following the American Revolution. This situation was resolved with the conclusion of the Louisiana Purchase. In the 1840s, westward expansion led to war with Mexico, which lost a vast swath of its territory to the United States in the Treaty of Guadalupe Hidalgo in 1848. In the late nineteenth century, westward expansion had two major effects. First, the west became a destination for millions of immigrants, both from the eastern United States and the rest of the world--from China to Ireland. Second, westward expansion increased the strategic and commercial role of the United States in the Pacific, a development that contributed to American imperialism in the late nineteenth and early twentieth centuries. Conflict between the United States and Japan over influence in the Pacific would erupt in war between the two nations in the 1941. Overall, westward expansion was a major factor in the emergence of the United States as a major world power by the end of the nineteenth century.