Very valid points, but I think your example is a little tangential in that I'm talking about societal structures, not an organisation where there is a need to coordinate. Societies are self-organising to some extent, especially in their local cluster. e.g.
Suppose you have a room full of 5 people building a bridge with legos. They're a small group and thus benefit from say the agility small teams provide. They finish their lego bridge in record time & live happily ever after.
If you need to provide lego bridges for 10 people though then you've got a choice: you can stick 10 people into the room and make them build a bridge twice as big, or you can have two rooms each building their own bridge in close proximity & benefiting from the speed of small teams.
Thats a simplification sure, but I feel societal structure (e.g. the mindset that makes canada's healthcare work) are to some extent imprinted in the people & thus apply regardless of the size of the border on some random map. If you stick another hospital on a map in Canada it'll work just as well.
As a side note, not convinced about the big company thing either. It can certainly be like that, but well managed its not inevitable. I work for one of the biggest companies out there & absolutely everything is split into ad-hoc ~7 man teams that have essentially absolute power over that project.
Bit fuzzy post/argument I know - apologies for that.