George Washington defended the importance of the executive branch and tried to establish the presidency not as a ceremonial figurehead but as an energetic leader. He also defended that the Presidential figure had authority over the members of the executive branch.
When he retired in 1797, he created the notion that the individual who held the office was not the president but the person who is vested in the office which means that change of power is important.
The decision to retire after serving two terms was a major precedent indeed, but perhaps an even more significant one was that he insisted he not be called "Your Excellency", which made the presidency far different than a monarchy.
It was actually a city state at first, Through conquest, trade deals, and luck/resources. They were able to become an empire. Also reorganization of the Roman Legion helped.