Coke is actually very different from country to country and less so from state to state. This is because Coke uses local bottle companies and they might be using different water. The coke you buy at your local store is probably bottled somewhere close to keep shipping costs down.
If you're a fan of Dr.Pepper, you'll notice they have 2 different bottles based on where you buy. That's because in some regions, Dr.Pepper uses Pepsi for bottling and in others it uses Coke bottlers.
Coke used to be mixed, bottled, and shipped out in an extremely quick timeframe. Inventory turned over fast.
I suspect the separated components wind up being equal to what a stale soda has, one that has been on the shelf. It’s like buying a soda whose sugar component has already gone stale.
Sure, the rest of the flavors are there and still fresh, unaffected by the carbonated water, but the sweetness one is off.
Honestly, the water is just a guess since the taste is different and the syrup comes directly from Coke. In other comments here, people mention the cans used but I’ve had Coke in glass from different countries taste different.
If you're a fan of Dr.Pepper, you'll notice they have 2 different bottles based on where you buy. That's because in some regions, Dr.Pepper uses Pepsi for bottling and in others it uses Coke bottlers.