The early expansion of United States territory and redefinition of borders had a significant impact on the relationship of the United States with other nations and resulted in political conflict.
One of the most notable examples of this was the Louisiana Purchase in 1803, in which the United States acquired a vast amount of land from France, which greatly expanded the size of the country and established the United States as a major player on the world stage. However, this expansion also led to conflicts with other nations, particularly Spain and Great Britain, over control of the newly acquired land and the borders of the newly expanded United States.
Another example was the Mexican-American War in 1846-1848, where the United States annexed a large portion of Mexico's northern territory, including present-day California, Nevada, Utah, Arizona, New Mexico, Texas, and parts of Colorado, Wyoming, Kansas, and Oklahoma. The annexation of the land, and the U.S. expansion into the southwest, led to significant political tensions between the U.S. and Mexico, which still affects the bilateral relations of both countries today.
Additionally, the forced displacement of Native American tribes and forced relocation of their communities as the United States expanded its territory also led to political conflict, as Native American tribes resisted the displacement and the U.S. government's policies towards them.
These conflicts and disputes over territory and borders were also rooted in economic and strategic interests, as the United States sought to expand its influence and control over valuable resources, such as land, gold and silver, and trade routes.
Overall, the early expansion of United States territory and redefinition of borders had a profound impact on the relationship of the United States with other nations and resulted in political conflict, as other nations resisted the United States' attempts to expand its territory and influence.