I was raised in Australia, i lived in England for two years, Canada for two years, and i’ve now lived in the United States for over a decade.
I simply can’t pick where an Aussie is from, based on accent alone, the way that i can with a whole bunch of Brits and Americans. I can pick a Liverpool accent from a Birmingham accent or a Geordie accent. At one time, i could tell Yorkshire and Lancashire apart quite easily, although i may have lost that skill. And north versus south in England is pretty easy, for the most part. I also know what a west country accent sounds like. And a bunch of others.
In the United States, i can pick some of the more obvious differences quite easily. It’s relatively easy to tell if someone is from the south, although i sometimes have trouble telling exactly where they’re from. Quite a few city accents like Boston and New York and Baltimore (and variations within those cities) are also familiar to me. I can also usually pick a Canadian accent, although most of my experience is in western Canada, and not in Ontario or Quebec.
I can’t make any of the same sort of distinctions in Australian. The best i can do, sometimes, is distinguish rural from urban. I grew up in the suburbs, but i went to an agricultural boarding school with a lot of kids from western New South Wales, and as a whole their families’ accents were a little broader or “harsher” than what i was used to. But even this isn’t an infallible guide, because plenty of working- and lower-middle-class people from city and suburban areas speak in pretty much the same way.
I’ve had people say to me in the past that they can tell a Sydney accent from a Melbourne one, or that they can definitely distinguish a unique Adelaide accent, but i just don’t buy it.
Interestingly, some of the most distinctive Aussie accents, to my ears at least, are to be found among post-WWII immigrant communities. Greek Australians often have a particular Aussie accent that is quite easy to pick. It has been parodied a lot on TV, often by Greek Australians, but i’ve known second-generation Australians of Greek background and their accent was both distinctively Australian but also distinctively different from “regular” Australian. Before i moved to the United States, i lived near one of the main Italian neighborhoods in Sydney, and many Italian Australians also had an accent that was clearly Australian but inflected by their ethnic background.