there are many differences between american english and british english in pronounciation and some idiomatic expressions, of course it differs state by state, for example new yorkers pronounce the words differently (Tawk,dawg instead of talk,dog or watta instead of water), as hellopanda77 said most americans pronounce the middle T in a word or in a sentence like D ( I wanna geda beder car for example), they usually drop the T at the end of a word in speaking, in most american accents you can clearly feel the pronounciation of the er sound but in british accent it's replaced by the schwa. + the British speak english louder and more clear than americans. one of the main differences that i can tell you is in the words like "all,call,wall,walk,allways...", the British usually pronounce "ol,coll,woll,wok,olways,..." instead of "al,kal,wal,wak,always" in american english. ...

I noticed the pronunciation of both are different. The British pronounce every word very clearly (especially their t's) while Americans reduce the sounds (t -> d) and mix them all together; therefore, people get confused or overwhelmed because Americans speak so quickly. The idioms used depend on the settings (school, work, etc.) Watch some TV shows or movies from the U.S. and you'll catch some of them.

it's a nice Q .. well check these websites .. may help ya: http://www.usingenglish.com/reference/idioms/ www.idiomsite.com/ and i'll wait for an answer from a native english speaker here .. :D