BRITISH ENGLISH vs AMERICAN
There are many differences in pronunciation between British and American English, but most of them are not very important. Here we are only going to write about the most important differences for an English student, to help understand the other accent better. (We will use the British phonetic symbols).
THE LETTER R
This is probably the most important difference. British people only pronounce the letter R when it is followed by a vowel. American people pronounce this letter always.
teacher /ti:tʃə/ /ti:tʃər/
A final Schwa is pronounced very very weak in both BrE and AmE, but if it happens at the end of speech (if after the schwa we pause or stop), then in BrE it often opens and becomes a sound very similar to / ʌ /, but in AmE it doesn't change.
teacher /ti:tʃər/ in BrE it sounds similar to /ti:tʃʌ / (but in the phonetic transcription we still use an : /ti:tʃə/
THE VOWEL (as in SOCK)
In American English this vowel is more open than in BrE, so it sounds like the British vowel
(as in "father" or "car") but short. [similar to Spanish
or Italian A].
In British English this vowel sounds a little bit similar to the vowel (as in fork) [a bit similar to Spanish or Italian O].
THE VOWEL (as in HUT)
In American English this vowel is more closed than in BrE, so it sounds a bit like the British vowel [similar to Spanish or Italian O]. In British English this vowel sounds a bit similar to the American vowel [similar to Spanish or Italian A].
THE CONSONANT -T-
In BrE this consonant sounds / t / in front of a vowel or between vowels. In American English it sounds / t / in front of a vowel, but it is flapped when it goes between vowels, like a quick / t / (we'll use the special symbol: / D / ) [it sounds like the Spanish or Italian flapped R, as in "cara"]
Peter /pi:tə/ /pi:Dər/
But in colloquial BrE that may also happens. The difference is that the sound / D / occurs only in colloquial BrE, but in AmE that is the only possibility when the T goes between vowels.
PRONUNCIATION OF THE LETTER -U-
In British English, the letter U sometimes sounds (but, fun, must) and sometimes sounds / ju: / (tube, music, stupid).
American people also pronounce this letter with (but, fun, must), but for many of the words with / ju: / , they use the vowel
stupid /stju:pɪd/ /stu:pɪd/
But this only happens with some words and not everywhere in America. Other words are pronounced with / ju: / like in BrE (music, cute, you, etc), and others may be pronounced with / ju: / or with , depending on the area or the speaker (new, Cuba, etc.)
THE VOWEL (as in CAT)
In BrE, this sound is something between and , in AmE this sound is usually longer and much more similar to . In fact, in some parts of the USA, the main difference between and is that the first one is short and the second one long, but the sound is almost the same. Also, in many parts this vowel is simply , not a different sound.
SHORT / LONG VOWELS
In BrE all the vowels can be classified as short ( , etc) or long ( , etc.). In AmE they are all the same in length, or the difference is much smaller than in Britain. The difference is usually made with a contrast between tense and non-tense pronunciation rather than long and short.
Another important difference is intonation. When we speak, our voice goes up and down. When English people speak, their voice can go very high and quite low. When American people speak their voice is quite flat, they do go up and down but not so much. So the effect is that British people sing a lot, and American people sound much more monotonous by comparison.