Yes, Matthew, I'm "weary" of saying that, too! I've been saying it for years, and nobody believes me...
Seriously, though...yes, of course there are many variants within English-speaking cultures, and some of these could conceivably be classed as dialects. Imagine a conversation between a dockworker from Glasgow and one from Kingston, Jamaica, for example.But that isn't the issue here. We're looking at this question from the point of view of the non-native learner. We're addressing the concerns of the italki members who regularly ask questions like "Which is easier to learn, British or American English?" or "Which is better, US or British English?".
These learners don't want or need to know about the differences between Scouse and Cockney, Appalachian or Ebonics. They just want to learn standard English for their studies, their jobs, travel and international communication. And what Phil, myself, and many other long-term regulars on this site are at pains to stress is that these questions don't need to be asked. They don't need to make a choice.
Another tendency worth mentioning (I hesitate to use the word "difference") is the use of "have/has got" as opposed to plain "have".
Whereas an AmE speaker would probably say "Do you have the time?", a BrE speaker would be more likely to say "Have you got the time?". But this is only a preference. The same BrE speaker might equally well say "Do you have the time?" the next time he asks that question.
Thank you for writing this mini-article, Phil. I think it's important for learners to realise not only how few supposed "differences" exist between standard AmE and BrE, but also how inconsequential these are.
A few other important differences:
1. In the US, we will only negate or contract "have" if it is an auxiliary verb, not if it is a primary verb. In the UK, they don't have this distinction.
US and UK: I've eaten breakfast, but I haven't started working yet
US: I have 5 bananas, but I don't have any oranges.
UK: I've 5 bananas, but I haven't any oranges.
2. In casual speech, British speakers will often use passive past instead of past progressive. Americans won't do that.
US: he was standing next to the door.
UK (casual): He was stood next to the door.
3. British people still sometimes use the word "shall", even in casual speech. In America, this word is almost completely obsolete, and is only used humorously or in certain legal contexts.
2. Chris said: In casual speech, British speakers will often use passive past instead of past progressive.Not true at all! We wouldn't want the italki community thinking that you could wander around the streets of London saying "I was taken" instead of "I was taking" or "I was eaten" instead of "I was eating". This is nonsense.
In fact, this non-standard usage is restricted to only two phrases: "I was stood" and "I was sat", both of which are considered rather ill-educated. Please don't assume that this standard British English, or that it's a grammatical pattern that can be used for any other verbs.
3. So what about shall? Yes, it is used by some people, but not as widely as Americans think it is, and not in the way that you think is. In modern English, it's basically just an alternative to 'should' in a question form, as in Shall we get pizza? rather than Should we get pizza? And the majority of younger people don't use it at all.