How did cultures of both Ancient Greece and Rome influence the political system of the United States?

Ancient Greece left the West a rich legacy. Part of that heritage is democracy, a representative system of government that differed from tyranny, the common system of political organization of ancient Greek states. It was born in Athens. From Rome, we got the institution of the Senate, a deliberative body that held much power in ancient Rome. The classical Greco-Roman culture is the bedrock of Western culture.