The full form of .US is ccTLD for the United States

.us is the Internet country code top-level domain (ccTLD) for the United States. It was established in early 1985. Registrants of .us domains must be U.S. citizens, residents, or organizations, or a foreign entity with a presence in the United States. Most registrants in the U.S. have registered for .com, .net, .org and other gTLDs, instead of .us, which has primarily been used by state and local governments, even though private entities may also register .us domains.

The United States (U.S. or US), officially the United States of America (U.S.A. or USA) and commonly known as America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territories, 326 Indian reservations, and some minor possessions. At 3.8 million square miles (9.8 million square kilometers), it is the world’s third- or fourth-largest country by total area. The United States shares significant land borders with Canada to the north and Mexico to the south as well as limited maritime borders with the Bahamas, Cuba, and Russia. With a population of more than 331 million people, it is the third most populous country in the world. The national capital is Washington, D.C., and the most populous city is New York City.