-Spelling: For example, words ending in -ence in American English are -ense, such as defense (UK) /defense (USA) and licence (USA), and words ending in -re are -er in American English, such as meter (UK) /meter (USA) and centre (UK).
Pronunciation: For example, Americans usually pronounce "th" as "s" or not, while British pronounce "t".
-Vocabulary: For example, Americans may use some words that don't exist in Britain, such as "jizz", "yoof", "gay" and so on.
-Grammar: For example, Americans may use some grammatical structures that don't exist in Britain.