The Impact of the Enlightenment
The Enlightenment brought a flowering of science and freer thought. In some cases, however, it also brought excess, such as the French Revolution
The Enlightenment birthed both a concept of liberty and governments that are based on it and secure it, as well as the scientific underpinning of the Industrial Revolution. The new Republic embraced and benefited from both of these children of the Enlightenment. Liberty, to include the economic liberty espoused in Enlightenment authors such as Adam Smith, and scientific inquiry, united with a culture that valued and rewarded individual efforts, produced a strong economy and a matrix in which people could excel to the limits of their potential.
The one salient exception was the "peculiar institution" of slavery that flew in the face of everything except the vested interests of plantation farmers and northern industrialists that wanted cheap cotton. Indeed, unfettered capitalism and greed, became one of the critical weaknesses of the new Republic and was the cause of governmental intervention and ultimately a civil war. Greed placed economic advantage over the principles of the Enlightenment and perhaps proved some of the critics of the Enlightenment correct and led to Karl Marx's observation that "capitalism contains the seeds of its own destruction".
The fundamental problem of the new Republic was that it drifted from its own ideological premise. The failure to abandon the "peculiar institution" and free the slaves almost certainly caused the American Civil War and the need for a Civil Rights movement and the concomitant expansion of the federal government and Constitutional amendments.
The question is whether this was a failure of the Enlightenment, the product of a Counter-Enlightenment, or simply a function of the natural proclivities of human nature. As noted elsewhere, the liberty generated under the Enlightenment did lead some to act on their own interests with little restraint, hence the term "libertine". However, since the gates of the Enlightenment swung shut shortly after the founding of the Republic through the excesses of the French Revolution and the Counter-Enlightenment, it is hard to say whether the drifting from the Enlightenment principles was a function of excess liberty or the natural result of the abandonment of the Enlightenment.
It is probably safe to say that the impulse toward ending slavery came at least in part from the notions of the founding of the Republic and hence the Enlightenment. Abraham Lincoln, in the Gettysburg Address, essentially confirmed it:
Four score and seven years ago our fathers brought forth on this continent, a new nation, conceived in Liberty, and dedicated to the proposition that all men are created equal.
Now we are engaged in a great civil war, testing whether that nation, or any nation so conceived and dedicated, can long endure. We are met on a great battle-field of that war. We have come to dedicate a portion of that field, as a final resting place for those who here gave their lives that that nation might live. It is altogether fitting and proper that we should do this.
But, in a larger sense, we can not dedicate -- we can not consecrate -- we can not hallow -- this ground. The brave men, living and dead, who struggled here, have consecrated it, far above our poor power to add or detract. The world will little note, nor long remember what we say here, but it can never forget what they did here. It is for us the living, rather, to be dedicated here to the unfinished work which they who fought here have thus far so nobly advanced. It is rather for us to be here dedicated to the great task remaining before us -- that from these honored dead we take increased devotion to that cause for which they gave the last full measure of devotion -- that we here highly resolve that these dead shall not have died in vain -- that this nation, under God, shall have a new birth of freedom -- and that government of the people, by the people, for the people, shall not perish from the earth.
These are exactly the principles of the Enlightenment as encoded into both the Declaration of Independence and the Constitution. Even the Constitutional amendments that followed the War were designed to further these goals. Clearly, the Enlightenment continued to have a significant impact well beyond the Revolution, even if there were no explicit references to it and many that subscribed to its tenets had never even heard of it. But they did know what the founding principles say so clearly.
Unfortunately, many did not follow through after the war and it took an additional century and vigorous government action and expansion to bring about integration and the true vision of the Declaration.