Final answer:
The Enlightenment of 17th-century Europe most directly influenced the framers of the U.S. Constitution, providing them with the intellectual foundation to craft the principles of American democracy and representative government.
Step-by-step explanation:
The Enlightenment of 17th-century Europe had the most immediate impact on the framers of the United States Constitution. This cultural movement introduced novel ideas about democracy, government, and individual rights, drawing from the intellectual currents of ancient civilizations such as Greece and Rome, but most decisively from the Enlightenment philosophes. The confluence of these historical influences established a foundation for the American democratic republic.
American founders such as Thomas Jefferson and James Madison were deeply influenced by Enlightenment thinkers like John Locke and Montesquieu. The concepts of self-government, natural rights, consent of the governed, and separation of powers that characterize the American system have their roots in these Enlightenment ideas. While ancient civilizations provided the early models of democracy and representative government, it was the Enlightenment's focus on reason and science that reshaped these concepts into the democratic traditions we recognize in the U.S. Constitution today.