The United States of America is a country located in North America. It is the third largest country in the world, both in terms of land area and population. The US shares borders with two countries, Canada to the north and Mexico to the south.

The US-Canada border is the longest international border in the world, spanning 8,891 kilometers. The border between the two countries is mostly defined by the 49th parallel, except for a small section near Vancouver Island, where it follows the 49th parallel. The US-Canada border is also known as the "International Boundary," and it is one of the most peaceful borders in the world.

The US-Mexico border, on the other hand, is 3,145 kilometers long and is the busiest land border in the world. The border is mostly defined by the Rio Grande River, which separates Texas and Mexico. The US-Mexico border has been a topic of controversy, particularly in recent years, due to issues such as illegal immigration, drug trafficking, and border security.

Aside from its land borders, the US is also surrounded by water on its east, west, and south coasts. The country is bounded by the Atlantic Ocean to the east, the Pacific Ocean to the west, and the Gulf of Mexico to the south. The US also has maritime borders with Cuba, the Bahamas, and Russia.

In conclusion, the US shares borders with two countries: Canada and Mexico. The US-Canada border is the longest international border in the world, while the US-Mexico border is the busiest land border in the world.