Well just yesterday I confused a man with from Australia for having a British (I meant English) accent, so I'm questioning whether I should take part in this. I also did the same thing to a Welsh man a while ago. In fact, because of that, I'd asked the man if he was from the British Isles at all (hoping I'd get a hit), and was still wrong.
See I have some attributions to certain accents. Because I'm from Canada, I'm exposed to a lot of accents, but more often than not I don't go around asking people where they're from, so I've got no way to make the phonetic differences for myself. I've never heard a Welsh man before, and I forget what that man sounded like as he only said a few words. And of course, like almost everyone, I've heard of the Crocodile Hunter, so I expect the Australian accent to be overzealous by nature.
I'm constantly assuming the accent has the following pronunciations; Water = Wowtah; Vi
ta(h)mins = Vitimins; Aluminum = Alyuminiyum.
And I'd be wrong, and I expect to have possibly offended some people. It's just how I've attributed the accents. Unless I have an extended conversation with someone, I wouldn't be able to determine if they are British-English (If I just said "English" that could apply to anyone that speaks the language), Welsh or Australian, and the same would probably be for Scottish/Irish. I'd just take a swing unless I heard some keywords.
Being a Canadian, and watching a lot of American TV and Canadian TV, I've found that you
could say there are differences if you're picky, but really, we sound a lot alike (no, I've never heard anyone say "aboot" and such, and "eh?" is sometimes treated as hillbilly talk). Oh, speaking of hillbillies (horrible term, I'm sorry), we have folk who have a Southern accent here in Nova Scotia. Little Nova Scotia, a peninsula not 12 miles from end to end.
But then you get mainland Nova Scotia mixed up with Cape Breton and you're asking for a fight, because Cape Bretoners are very found of their Gaelic heritage, and I can recognize a Cape Bretoner off the bat, but I'd be quick to call a Scottish/Irish person a Cape Bretoner, rather than them being Irish/Scottish. On the mainland we've got a very general Eastern North American accent, which is what people attribute to being the "American accent" around here. And Newfoundland's not part of the maritimes, it's Atlantic, and a whole bunch of local accent/dialect issues.
...See? We take big deals in our local accents, but globally, I imagine we all make little mistakes like that. Well, with the acception of a Welsh or English man confusing an Australian for one of them, and so forth (whatever so forth is in this case).
Geez... I didn't think I'd go on for so long.
So, just to be clear, the accents I get confused often (there may be others but I wouldn't know them because I don't know a lot of people with accents)
Irish/Scottish/Cape Breton
English/Welsh/Australian/New Zealand
Eastern American/Middle American/Southern Canadian (as in most of the Can. Population)
Nordic/German
...I think that's it. I can imagine I get a lot of vice for that, but I've never been further than Montreal... Oh don't even get me started on Quebec/France. Don't even.