求英文介绍美国环境

The United States is situated almost entirely in the Western Hemisphere: the contiguous United States stretches from the Pacific Ocean on the west to the Atlantic Ocean on the east, with the Gulf of Mexico to the southeast; it is bordered by Canada on the north and Mexico on the south. Alaska is the largest state in area; separated from the contiguous United States by Canada, it touches the Pacific on the south and the Arctic Ocean on the north. Hawaii occupies an archipelago in the central Pacific, southwest of North America. After Russia and Canada, the United States is the world's third or fourth largest nation by total area, ranking just above or below China. The ranking varies depending on how two territories disputed by China and India are counted and how the total size of the United States is calculated: the CIA World Factbook gives 3,794,083 sq mi (9,826,630 km2),[1] the United Nations Statistics Division gives 3,717,813 sq mi (9,629,091 km2),[16] and the Encyclopedia Br