> The only consistently working, stable democracies do not have a single leader of the executive branch, e.g. Switzerland.
That system had to develop organically over many generations to be successful (in the case of Switzerland it was 500+ years with only a few significant interruptions) . In a centralized country with no traditions of communal and local politics it can just result in chaos.
The system we had in the US pre New Deal was much more like Switzerland. Decentralization works just fine out of the box. The problem is that human instinct tends towards power which requires more centralization to accumulate.
The system was introduced around 170 years ago and it was done very suddenly after a civil-religious war won by protestant liberals.