I’ve gone through the JSON file containing all of the English names in the game, and I’ve noticed that there are many more world names than city names. Lots of world names are names of cities, but they are not city names in the game (Eg, “Independence” is a town in Oregon and Rhode Island, it is a world name, but but not a city name as well)
I haven’t tested the game with a world name being both a city name, but I’m guessing that this is because that would cause the game to crash upon generating a world, or because lots of world names were names of cities before cities were implemented into the game.