To continue with the simple population density idea maybe there's a ratio hidden here. Over long time frames.
(Total population size vs population density) would be a chart of sustainable accountable governance. Also maybe amplified by the speed of information.
Probably a sweet spot and a breaking point*, could make some obvious predictions with this.
Geographically large dispersed populations will be unstable and require increasing force to maintain.
Small or higher population density states will be more stable with a more accountable government. Within the carrying capacity of the land mass. ireland switzerland....
By this logic russia australia and canada will become the worst nations for it's citizens long term until they break up, even considering the population clustering.
Not sure if there would be a breaking point in the other direction? Extreme high population density. Probably not relevant yet. ( Until self sufficient dyson cylinders..)