America

The Americas, or America also known as the New World, are the combined continental landmasses of North America and South America in the Western Hemisphere. Along with their associated islands, they cover 8.3% of the Earth's total surface area (28.4% of its land area). The topography is dominated by the American Cordillera, a long chain of mountains that run the length of the west coast. The flatter eastern side of the Americas is dominated by large river basins, such as the Amazon,Mississippi, and La Plata. Since the Americas extend 14,000 km (8,700 mi) from north to south, the climate and ecology vary widely, from the arctic tundra of Northern Canada,Greenland, and Alaska, to the tropical rain forests in Central America and South America.

United States

The United States of America (USA), commonly referred to as the United States (U.S.) or America, is a federal republic consisting of 50 states and a federal district. The48 contiguous states and Washington, D.C., are in central North America betweenCanada and Mexico. The state of Alaska is located in the northwestern part of North America and the state of Hawaii is an archipelago in the mid-Pacific. The country also has five populated and numerous unpopulated territories in the Pacific and the Caribbean. At 3.80 million square miles (9.85 million km²)and with over 320 million people, the United States is the world's fourth-largest country by total area and third most populous. It is one of the world's most ethnically diverse and multicultural nations, the product of large-scale immigration from many countries. The geography and climate of the United States are also extremely diverse, and the country is home to a wide variety of wildlife.