Cross-border questions...

Accents in the northern United States are very similar to those in the adjacent areas of Canada, though honestly there isn't a lot of difference between US and Canadian English in general.

I don't know, zZigzZag. When you drive from Southern Ontario into Buffalo, New York, you notice the difference. The way the Western New Yorkers pronounce dollars, Topps and other words with "o" is undeniably different and distinct. I can tell from the first few words which side of the border someone is from.

The differences in the North Western US and South Western Canada are certainly very close, though.

There is a feature of Canadian (eastern only?) English that really stands out to me. It's the vowels sound in "hands" "can" etc. I am pretty sure that people from Upstate NY have the same way of talking. But I know a NYC person who talks the same way, and it confuses me. Maybe it's part of the NYC accent and I didn't realize it sooner.

Oh and regarding "dollars", I can always spot a Canadian when they say things like "doe-llars." Watch Jeopardy and listen to how Alex Trebek says it. Is that Canadian in general, or more of an eastern thing?

In Europe we have more exciting examples of transitional dialects between different languages. I once started in Prague and headed due East through Slovakia, Transcarpathia into Ukraine, then on to Kiev. Although the languages Czech - Slovak - Ukrainian - Russian are distinct, there are many transitional dialects, so you're not aware of a jump discontinuity and nobody has trouble understanding neighbours from up to 100 km away, even if they theoretically speak the same lanaguage.

Andrew, though I speak absolutely NO Polish, I noticed that a Silesian friend of mine, whose native language was Polish, used a number of words that were somewhat German. For example, there was one which sounded like Kartoffeln for potatoes. I subsequently discovered that this was not the regular word for potatoes in Poland. I suppose this is a variety of the same thing; at the time I put it down to the fact that Silesia has been an area of shifting borders.

I think counties do have distinct language borders, i live a few miles from the border of south yorkshire, and there is a definite change in accent to a broader yorkshire accent only a few miles up the road. I also think this is the case in other places, otherwise you wouldn't be able to describe someone as having a lancashire/somerset/cornish etc accent.

I also think the country border distinction is not as strong as you make out (although it is strongre than country differences). I know a few people from buckley, a town a few miles inside wales, their accent it somewhere between scouse and north welsh and definitely represents a mix of the two.

queenslanders speak s.l.o.w.e.r, but no accent change, we all speak 'strain'

I can definitely hear the difference between south western German and Swiss German. I can't between south Bavarian and north Tyrolean though.