To understand this you must understand that humanity has risen to various states of high technology at least several times in the past.
So let's say aliens come and attack us tomorrow and wipe out 99% of the human population. The survivors would be knocked back to primitive living. All the stuff we have today lost with the engineers, scientist, etc. Our satellite grid, electric grid, skyscrapers technology, everything lost. We'd be back to the stone age.
And keep in mind it wouldn't be just America knocked down, but Russia, China, africa, middle east, all of humanity. You'd have pockets of people living the tribal, nomadic, hunter gatherer life for a thousand years.
Our descendants would come across remains of our technology and not know what the fukk it is.
When our descendants finally start rising again in like 3,000 years, they'll dig up like...Disney World trash and be like
"who built this ,where they got this tech from to do this 3,000 years ago? We thought we were the pinnacle?" They find a label or stamp with Walt Disney on it and guess "Oh, this was a civilization called Walt Disney".
So not going any further, but see how that work? Atlantis wasn't a country. It was a global civilization of people who had cities and territories on every continent. Kinda of how America does today. But we don't have a patent on skyscrapers, electricity and other things like that. All these countries have their own version. Just like buildings in other countries have their own swag, pyramids in various locations have their own swag.
We get caught up in the race game and are looking at a tree instead of seeing the forest.