From PBS: The differences between American and British are not due to Americans changing from a British standard. American is not corrupt British plus barbarisms. Rather, both American and British evolved in different ways from a common sixteenth-century ancestral standard. Present-day British is no closer to that earlier form than present-day American is. Indeed, in some ways present-day American is more conservative, that is, closer to the common original standard than is present-day British.
Some examples of American conservatives versus British innovation are these: Americans generally retain the r-sound in words like more and mother, whereas the British have lost it. Americans generally retain the ‘flat a’ of cat in path, calf, class,whereas the British have replaced it with the ‘broad a’ of father. Americans retain a secondary stress on the second syllable from the end of words like secretary and dictionary, whereas the British have lost both the stress and often the vowel, reducing the words to three syllables, ‘secret’ry’. Americans retain an old use of the verb guess to mean ‘think’ or ‘suppose’ (as in Geoffrey Chaucer’s catch-phrase ‘I gesse’). Americans have retained the past participle form gotten beside got, whereas the British have lost the former. (The British often suppose that Americans use only gotten, in fact they use both, but with different meanings: ‘I’ve got a cold’ = ‘I have a cold’ and ‘I’ve gotten a cold’ = ‘I’ve caught a cold’).
AMERICANS SPEAK cLOSER TO REAL ENGLISH COME AT ME