To be certain, both citizens of America and France defend their respective revolution as being most important, and with good reason. I don't expect Americans in today's society to proclaim the French Revolution as more important to world history, nor do I expect the French to think of America's revolution in the same light either. The growth of nationalism in the 20th century would make such an inquiry virtually impossible.
Instead, I would like us to understand these revolutions from the perspective of the participants. If we were to travel back in time to 1789, there can be NO QUESTION that the citizens of America and France (along with most of Europe) would be hailing the French Revolution as THE MOST IMPORTANT movement of their era. Virtually nobody would think to include the Constitutional Convention in such an argument. After all, America was a frontier nation, not the sophisticated world of France!
With this said, however, as the French Revolution wore on, more and more Americans began to see the American Revolution through a different lens. As the events of "The Terror" and other violent outbreaks began to ravage the French countryside, the differences between the motivating factors for revolution in America v. France became much more clear. As one historian put it:
Unlike the American Revolution, whose philosophical ancestors were the English liberals, the French Revolution was fundamentally fathered by the French radical philosophers, especially Jean Jacques Rousseau, and inherited the faith in reason engendered by The Enlightenment. RenŽ Descartes' trust in geometric like reasoning and Rousseau's belief in the common will and sovereignty of the people framed the conception guiding the French Revolution. This conception is mechanical. Government is a machine, fueled by coercive power, and driven by reason; and its destination is Social Justice. Government is thus a tool to reach a future goal -- improving man. Those in charge of the State would therefore use reason to apply government to further and create Social Justice.Despite the motivations for instigating revolution, there can be no mistaking the fact that these two revolutions, both of extreme importance to world history, had very different conceptions.
This conception is clearly different from that of the American revolutionaries. For the Americans, interests were the guiding force; for the French, reason. For the Americans, Freedom was to be preserved against the State; for the French, the State was used by reason to achieve Social Justice. For the Americans, individual rights were essential to protect interests; for the French, the collective, the sovereignty of the people, the general will stood above rights. Finally, for the Americans, no one interest could be entrusted with the State -- all interests had to be limited and balanced by their opposition; for the French, the State was a tool that should have no limit so long as Social Justice was pursued according to the common will.