As an example, swiss cantons are considerably more independent from the Swiss Confederacy (i.e. what most people know and call 'Switserland' the entity) than the states of the USA are.
As an example of how far that goes: Switzerland essentially does not have a capital. The cantons usually do, though. Bern is the seat of the Federal Assembly and is usually considered the capital, more because social norms and systems are based on the notion that all countries must have one.
Swiss cantons can work together and often do, but evidently, not on this.
And three republics! Geneva, Ticino, and Neuchâte.
It's crazy to have 2100 distinct municipalities? The site isn't showing "here are 2100 different email hosts that municipalities in Switzerland use," but rather "here are the 2100 municipalities in Switzerland, and if you click you can see what host each one uses."
There's plenty of overlap, just from a cursory look.