What wars were the United States involved in between 1800 and 1863? What nations did the United States fight? Why did we fight these wars (explain for each)?

The United States was involved in dozens of different conflicts in the nineteenth century, some of which involved defending its frontiers or expanding its territories and others which were in support of allies or commercial interests in other areas. Some of the major wars in which the United States was involved include the following:
Barbary Wars (1801-1815): These wars were fought against the "Barbary pirates" in North Africa who preyed upon shipping in the Mediterranean. The United States had been forced to pay tribute to guarantee American merchants safe passage but eventually chafed under this. The United States then built up its naval forces and joined with several European nations to fight against the pirates.
American Indian Wars: The Unites States, as it expanded westward, often gained territory by military conquest, attacking any Native American tribes who resisted being displaced or having their lands colonized. These were basically wars of territorial conquest.
War of 1812 (1812–1815): This was a war against the British. The British tried to invade the United States, and the United States attempted to invade Canada, which was a British territory at the time. It ended in a stalemate and the Treaty of Ghent.
Mexican–American War (1846–1848): This was a war between the United States and Mexico over territory that now comprises the southwestern United States but was then part of Mexico. The treaty ending the war located a new border on the Rio Grande and added California, Nevada, Utah, New Mexico, Arizona, Colorado, and parts of adjacent states to the United States.
American Civil War: This was an internal conflict between US states.