A student is learning British English. He wants to know whether he can talk to Americans, what American English is and how important these differences are.
Of course, there are some differences between British English and American English. There are some differences in grammar. For example, people who speak British English say "in the hospital" and "Do you have a pen?" . Americans say "in the hospital" and "do you have a pen?" . Pronunciation is sometimes different. Americans usually pronounce the "r" in words such as "car" and "farm". Some people who speak British English don't pronounce the r in these words. There are differences in spelling and vocabulary between British English and American English. For example, "color" and "favorite" are British English B spellings, and "color" and "favorite" are American English A spellings.
However, these differences in grammar, pronunciation, spelling and vocabulary are not important. To a great extent, British English and American English are the same language.