The correct answer to this open question is the following.
Both the Enlightenment Philosophers (Hobbes, Locke, Rousseau) and Greek/Roman Democracies have shaped the U.S. Constitution and form of government in the following way.
Ancient Greek has influenced the United States in the concept of Democracy. It was the people from Athens who developed this new form of government in ancient Greece. The Roman Republic influenced the United States in the concept of law. The Roman Law was very effective for the time, and many concepts have shaped the US legislation.
Enlightenment philosophers such as Hobbes, Locke, Rousseau influenced the United States independence movement with their ideas of liberty, society, and government. These ideas influenced the US founding father such as Thomas Jefferson, Roger Sherman, and Benjamin Franklin when they drafted the Declaration of Independence. Then later, Enlightenment ideas also influence the creation of the US Constitution during the Constitutional Convention of 1787 in Philadelphia, Pennsylvania.