There are --MANY --SMALL --UNIMPORTANT differences. Here are a few examples. Spelling: British "colour," U.S. "color." British "theatre," U.S. "theater." Vocabulary: Fuel for a car, British "petrol," U.S. "gasoline" or "gas." Baby "nappies" (British), "diapers" (U.S.) Grammar and usage: Differences are MOSTLY a question of FREQUENCY. Many "British" usages are correct but RARE U.S. usage and vice versa. British: "I have already eaten." U.S.: "I already ate." British: "He's in hospital," U.S. "He's in THE hospital." Pronunciation: Jaguar, British "Jag-war," U.S. "Jag-you-are." Garage, British "GARridge," rhymes with "carriage." U.S. "gar-AZH" (i.e. more like the French pronunciation). For a very thorough article, see http://en.wikipedia.org/wiki/Comparison_of_American_and_British_English

"What is the difference between...?" Knock yourself out, my friend! :D http://en.wikipedia.org/wiki/Comparison_of_American_and_British_English