The English Civil war 1642–1651, and the pro-parliamentarians led by Cromwell, and the Glorious Revolution of 1688, and English Bill of Rights of 1689, using the ideas of Locke's Second treatise(same year), were most important for laying the foundations of the ideas of liberal democracy. Of course, the Magna Carta is also a precursor.
The only thing making the U.S. Constitution unique is that the U.S. was the first major country to be explicitly founded as a Republic, and the first country to overthrow a monarchy. The South American revolutions against Spain were pretty explicit copies of this example - Simon Bolivar, for example, loved Thomas Jefferson, and actually sent his nephew to the University of Virginia. (The Monroe Doctrine was originally about preventing re-colonization of the independent Republics. It's too bad the U.S. did so many evil deeds in the Cold War)
The two intellectual groups involved in the founding were the Democratic-Republicans, led by Jefferson, and the Federalists, led by Hamilton. The Federalists basically, more conservative and sought a close emulation of Britain, were slightly elitist and monarchist sympathizing, and of course, wanted a strong central government. They elitism eventually proved unpopular, but they kept a stronghold in the Supreme Court with John Marshall (the Jeffersonians opposed Judicial Review)
The Jeffersonians were more radical, favoring a weaker federal government and individual rights. Thus they were instrumental in the creation of the Bill of Rights. They tended to favor France and had more diplomatic connection with them. The most radical founding father, Tom Paine, went to France to help the revolution, and narrowly escaped execution in the reign of terror for being a "reactionary".