In What Hemisphere is the United States? It depends on how you choose to cut the world in half. Hemisphere literally means half-sphere.
If you bisect an imaginary earth into northern and southern halves (at the equator), the USA is located in the northern hemisphere, which contains almost 90% of the earth's population. The northern hemisphere consists of Asia, Europe, North America, Central America, a small part of South America, and about two thirds of Africa.
On the other hand, if the earth is sectioned into east and west (divided at the prime meridian), then America is located in the western hemisphere. The western hemisphere generally refers to the Americas, including associated islands like the West Indies and Greenland.