I love the imagination behind your questions
Thanks
but there are some tough "if's" to overcome in order to give you a somewhat educated answer.
If Plato was indeed not writing fiction...and if the atlanteans were real...and if they were indeed off the coast of Morroco...and if they still their uber-Pompeii catalysm... you see what I mean?
Which POD are you most interested in learning about?
Fair enough, perhaps I should have outlined more - I'll do it here and then edit the OP.
Based on the premise that Atlantis was "sunk", there is a suggestion that a Tsunami hit the Souss-Massa plain (the problem is, when? I guess we'd have to go pre-Plato). So at the very latest we'd have seen a tidal wave in the 360+ BC. I'd speculate at 400BC just because then it has had a long time for the news to move, and for some of the facts to be distorted. - Feel free to suggest a better one, I would probably go back as far as 1000 BC. I'd need to find more info on the hypothesis before throwing anything more specific - I apologise for that. Shall we go with that there was a
Admittedly, I'm waiting for someone to shout Atlantis = ASB and move this to the ASB forum.
So one of the suggestions in the hypothesis is that the Amazigh/Tuareg peoples are descendents, or former had contact with the Atlanteans, hence why they call the region an island.
Personally, based on potential fishing, and the population of Ancient Greece at this time (for a comparative population) - we could assume a hypothetical Atlantis of 1-2 million people spread across their Empire, probably clustered around the Souss-Massa plain with a few hundred thousand people, mostly concentrated along the coast, in the core territories themselves. Probably a significant amount in the city itself. Assuming that IOTL the core territories were devastated by a Tsunami, that wiped out the vast majority (99.5%) of the population, the remainder dispersing into the now independent peoples, or the Amazigh.
The PoD could well be that a significant part of the community had migrated inland along the Massa River, out of the range of the Tsuanmi (exploiting mining opportunities, or farmland, if this ever gets more that lightly speculative I'll expand on it) This ensured that when the Tsunami hit, Atlantean civilisation survived in this region, with perhaps 60,000-100,000 people across the region. The utter destruction of the economic core of the 'Empire' still effectively destroys it, so the populations outside the Empire are absorbed/killed by their neighbours. However, there are enough survivors in this uplands region to maintain the majority of their culture, and begin rebuilding.
Assuming that this all happens in the aftermath of a Tsunami in 1000 BC that wipes them out as a military superpower, and that they aren't any more advanced than the Achemenids were, beyond having more widespread use of iron, and a longer memory - say they were one of the first, adopting iron in 1350 BC. They're devestated, but they have a substantial population to rebuild from.
Well, if there are and if there are enough of them to rebuild, you've basically got a Carthage a millennium early, without much in the way of competition except behind it in Greece and Egypt and the fertile crescent;
give them time to grow and that's going to be a western Mediterranean centred maritime largely- mercantile empire stretching across the Atlantic shores of Europe and Africa.
The old mesopotamian nations are going to be well plugged into this, they're where the markets are, but it for one thing gives Rome and any other upstart a much rougher start, they would be at much more of a disadvantage against the atlantean empire. So would Athens, for that matter.
Africa probably becomes stronger in the long term, Europe weaker; question then becomes how long they can hold their grip, when does overstretch become an issue? The known world, and the stage, become bigger.
Hmm, I dunno about it being Carthage - lets not pretend that this suddenly magics trade partners into existence - the majority of their trade partners could well have been their nomadic neighbors, or their own colonies scattered across S.W Europe and Africa and beyond them, Mesopotamia. In fact, if Athens was being invaded when this all happened (as Plato suggested), then they may never have gone that far east, instead trading with intermediaries such as the Minoans, Egyptians, Greeks, probably through non-Atlantean trade posts in Italia, or closer to home - could be an interesting counter narrative to the Greek and Phoenician colonies going west.
Admittedly this is starting to get difficult to juggle, so I may have to think some more of this through, but we could well use this 'Atlantis' to explain some of the less sure parts of history, such as the Sea Peoples.
Though touching on Thera - it could be that the Minoans were the survivors of the Atlanteans out East, and that they just suffered a tragically similar fate to their homeland.
Hrmmm - Perhaps I need to hammer out a scenario - and whilst I don't intend to make them super-men, being one of the first with Iron and a colonial Empire at that point in time will probably be more comfortable to discuss in the ASB section.
(Dammit, why can't there be a Crypto-History section?)