The United States of America is a political entity on the North American continent on Earth. Established in 1776 by declaration of thirteen states, it eventually grew, by 2033, to include 52 states. (TNG episode "The Royale")
The United States remained a distinct political entity into the 24th century. The President of the United States of America was one of the officials who toured San Francisco in the aftermath of the Breen attack during the Dominion War. (short story: "Eleven Hours Out")