Students should not be concerned about any differences between British and American English.
When recording cassettes for students and teachers, I use actors with both American and English voices. They provide a variety of differences in pronunciation and intonation which it is useful to get used to.
But if you ask me if there are structural differences between American English and British English, then I have to tell you, "No, not that you would notice."
Of course, you get these variations of vocabulary that people make much of, and some are listed here. But I would say there is a greater difference between the class and regional dialects within each country than there is between the educated speech of San Francisco and London.
The real problem is to understand a Southerner from the Louisiana bayou country, or a Liverpudlian from Toxteth, or a Glaswegian.
There is the odd word that can cause difficulties. Years ago, teaching a class of teenagers in Montreal, I learnt quickly that what the English call a rubber, the North Americans call an eraser. A rubber in North America is a colloquialism for a condom. Asking a student if I might borrow his rubber was an invitation to loud laughter and coarse comment.
Another student was always late. I asked her if she couldn't get someone to knock her up in the mornings. Collapse of class. In England, it means to wake someone up, but in North America, to get a girl pregnant.
But, I repeat, the differences, the real differences, between British and
American English are slight, and the one borrows from the other constantly. Americans are perhaps more inventive, however. Recently, we have had "zipperwatch", a marvellous word to describe a reporter who is assigned to check on the sex-life of a politician; more recently, "bimbo", an attractive girl of limited intellect.
A few, largely time-worn, examples of British/American vocabulary differences (the British version is given first):
caretaker/janitor, council school/public school, public school/private school, dust cart/garbage truck, ex-serviceman/veteran, lift/elevator, fanlight/transom, holiday/vacation, pram/baby-carriage, pig breeding/hog raising, queue/line-up, scribbling-block/scratch-pad, tap/faucet, veranda/porch, timber/lumber
