With a population of 300 million or so, and a language that has borrowed from nearly every other language in the world, American English is has dozens of accents and dialects. Some vary from region to region, state to state, county to county, and even neighborhood to neighborhood. George Bernard Shaw’s Professor Henry Higgins would have a grand time sorting them all out.
An accent generally refers to how words are pronounced. Dialect is more of a mini-language, incorporating the accent, but adding expressions and phrases unique to itself. American English can be very roughly divided into the following dialects: New England, Mid-Atlantic, Southern, Midwestern, Upper Midwestern, Western, Northwestern and Californian.
American English often takes its dialects and accents from the language roots of the first settlers in the area. There is something very British about the way people from Massachusetts or Pennsylvania pronounce certain words. Those in New York sound perhaps more guttural, owing to their strong German and Eastern European influences.
Southerners sound mostly alike to non-Southern ears, but a native has no trouble distinguishing a mountain accent from one hailing from the Tidewater area of Virginia. The Southern accent is deceptively complex, borrowing as it does from the British accent, Scottish “burr” and Irish “brogue,” the Cherokee language, and mixed with slurred French intonations and staccato Spanish and spiced with African-American speech.
The Midwestern accent is usually considered the most “correct” of accents in American English, since it lacks a great deal of specific inflection, and sounds "flat." Upper Midwestern English takes its sound from the Scandinavian accents of those who first settled there.
The western accent of American English has Southern inflections, mixed with the Midwest accent of those settlers who made the trek with the wagon trains. The Pacific Northwest residents have western accents tinged with those of their Canadian neighbors in Alberta and British Columbia, just over the border. Californians tend to have less specific “accent” than other Americans, although when they do, it sounds more western. Southern Californians, like those raised in New York City, tend toward rapid-fire speech, and mix in the latest slang.
American English is so distinctive that it marks its speakers anywhere they travel. Many world citizens who have never traveled to the United States know an American immediately. Some people can even hazard a guess at where in the States an American lives by the accent.
However, the dialects and accents of American English also create walls among its speakers. American citizens are often stereotyped among each other because of how they speak. Dialect coaches make a great deal of money training actors to speak properly, not because they do not speak clearly, but because they use an unacceptable accent. Some Americans are considered ignorant or uninformed by their countrymen because of their particular brand of American English.