Despite the fact that Americans and the British originally spoke the same language there are a lot of things that differ between these two varieties of English. Even though people can fully communicate and understand one another quite well, there are some aspects of language where comprehension breaks down. Among them are vocabulary, pronunciation, grammar and spelling.
The basic difference lies vocabulary level. Whereas the British have petrol , the Americans call it gasoline; while the British drive lorries, the Americans drive trucks; the Americans pay checks, whereas the British pay bills; the British eat chips, but the Americans eat French fries and so on. Furthermore both groups of people will often use the same words , however these words denote totally different things. This problem creates much cause of misunderstandings, especially to people who learn English as a second language.
Another important factor which separates British and American English is the pronunciation. Not only is the American pronunciation more nasal, but also they are said to speak more carelessly, which in my opinion is not true. Unlike the British , the Americans pronounce -r in last syllables, the example of which can be words like weather, sweater, soldier etc. What`s more, -t- between vowels is voiced in the American variety, for instance writer, water or a lot of. Besides, the Americans use /a/ instead of British /o/: (hot, got, odd) and in the same way they replace British /a:/ with /ae/-“ash” in words like castle, can, dance etc.