When English novels are published in the United States, apart from the cover and illustrations, there are usually some differences in words, such as the different spellings of some English and American words. The biggest difference between the English version of Harry Potter and the American version is the first philosopher's stone. The English version is titled "Hewlett-Packard and the Philosopher's Stone", while the American version is titled "Hewlett-Packard and the Philosopher's Stone", and the American version clearly states that Dean is a black boy.

The specific differences are listed on the HP Dictionary website:

http://www.hp-lexicon.org/about/books/differences.html