American English

American English, or US English, is the dialect of English that is spoken in the United States. It is different from other types of English like British English. Most types of American English came from local dialects in England. During the 18th and 19th centuries, pronunciation changed less in America than in England.

 Use 
Many people today know about American English even if they live in a country that speaks another type of English. They hear and read American English through the media, such as movies, television, and the Internet, where the most common form of English is American English.

Because people all over the world use English, many new words are used. English has been changing that way for hundreds of years. For example, the millions who speak Indian English frequently add American English words to go along with its British English base and many other words from the various Indian languages.

Some people learn American English as it is spoken in the United States. For example, in telephone call centers in India and other places, people often learn American English to sound more like their customers who call from America. Those people often keep using American English in everyday life.

 Spelling 

There are many words that sound the same in both American and British English but have different spellings. British English often has more traditional ways of spelling words than American English.

 Vocabulary 
There are also some words in American English that are a bit different from British English.:
 aeroplane is called "airplane"
 ladybird is called "ladybug"
 lift is called "elevator"
 toilet is called "bathroom", "restroom" or "comfort station"
 lorry is called "truck"
 nappies are called "diapers"
 petrol is called "gas" (or "gasoline")
 the boot of a car is called a "trunk"
 a dummy is called a "pacifier"
 trousers are called "pants"
 underground is called "subway"
 football is called "soccer"
 braces are "suspenders" ("suspenders" in British -English are a type of clothing that is worn around the lower leg to stop socks/sox from sagging or around the upper leg by people wearing stockings)

 Regional accents 
General American English is the kind most spoken in mass media. It more vigorously pronounces the letter "r" than some other kinds do. Non-rhoticity ("R"-dropping) is frequent in certain places in which "r" is not pronounced after a vowel such as in the words "car" and "card," which sound like "cah" and "cahd" in places like the Boston area. 
Here are some regional accents of American English:

Appalachian English - This is the stereotypical hillbilly accent, is completely rhotic, and can even add "r" in words such as "warsh" for "wash."

General Southern - This is a range of accents tending to be rhotic or semi-rhotic and to have glide deletion in which "I" is converted to broad "a."

Tidewater English - A non-rhotic ("r"-dropping) southern variety that also has a "Scottish" or "Canadian" raising of the "ow" diphthong in words like "house," "about," and "brown."

Charleston and Savannah English - Almost extinct, these accents that are non-rhotic

Boston English (also East New England English) - This is the most famous non-rhotic American accent, and most other non-rhotic American varieties often get compared to it. Aniother Bostonian feature is the limited Canadian raising of the "ow" diphthong before voiceless consonants in words like "house" and "about."

New York City English - One of the most recognizable dialects in the US, it is characterized by variable non-rhoticity or semi-rhoticity and a rounding of the long o sound, making "coffee" and "thought" sound like "cawfee" and "thawt."

South Louisiana English - This group of non-rhotic accents can be heard in New Orleans and its surrounding areas. It can be described as a combination between New York City English and Southern American English.

Northern Midwest English - This area has accents that tend to sound a lot like Canadian English.

Valley girl and surfer dude - This accent is common to Southern California and has features like "vocal fry" (creaky voice) and "upturn" at the ends of sentences.

 References 

 Other websites 
 American English -Citizendium