Toward a Theory of Country Size
It is well known that following consolidation, during which it might have looked as if countries were destined to combine into a few supercountries, we entered a period of secession and disintegration, with the number of countries growing. One puzzle associated with this is why there are so many federations. What follows is the beginning of a theory of size and confederation - and I look forward to comments before putting this in the form of a full-blown theory.
My starting point is that resources are not spread evenly across regions, so that when one part of a country is rich (as from salt deposits (long ago) or natural harbors or oil reserves), it will prefer to be on its own in order not to share its wealth with a larger group. But of course these pockets of wealth will be vulnerable to attack (trade wars and embargos for starters, but then military invasions too) if they are on their own and not in reliable alliances. "Optimal" country size is thus about compromising security (which is positively correlated with size) with the cost of sharing valuable resources. Risk averse people might agree on a large country size if they did not know whether they would be rich or poor, but once they discover regional wealth, that region can be expected to be exploited.