The linguistic style and phonetic patterns used in vocal communication native to a relatively small portion of the United States of America.
General American was considered "accentless", by most people in a nation wide study. Though technically it could be called an accent.
General American is also known as the Midwestern Standard, because it is spoken most frequently in parts of the Midwest including most of Nebraska, Iowa, parts of central Illinois, and NE sections of Kansas and Missouri. In is most common in this region but is also widespread, esp. umong the upper class.
General American could be considered the American Equivalent to the Received Pronunciation (the British accent in most Hollywood movies) in England.
Newscasters and TV stars are generally taught the General American accent because it is most widely understood in all parts of the country.
Bob, from Omaha did not understand his cousin Jeffrey from New Orleans when he spoke because he did not use the Midwestern Standard.