It turns out that most American thinkers, both of the left and right, are "liberals" in the sense of John Locke - people who respect human rationality, religious tolerance, the importance of education, property rights, and so on, and who care deeply about such basic ideas as liberty and equality.
It also turns out that the concepts of liberty, on the one hand, and equality, on the other, aren't exactly the same thing.
(Think of the need of factory owners to employ children in order to keep their costs down. Must their liberty to do so be ensured? Or think of blacks seeking to join American society as equal members. Must their equality be ensured?)
What we have here are two versions of American liberalism - A view that believes that a national government must never be a big, activist government, in order to protect individual liberty, or a view that believes a democratic government must actively promote equality and use its powers to do so because there is no other way to do what is right. These days we call these versions "conservative" and "liberal."
There have been other ideas in America - socialism, religious authority, etc. - but they have never really supplanted liberalism in this country. (Ronald Reagan tried to bridge the gap - liberal ideas of individual freedom linked uncomfortably to conservative religious ideas of 400-year-old folks like Winthrop and his City on a Hill, where freedom only involves what the church masters inform people about what God wants. You are free, but only to do that will.)
Still, the U.S has had a great run. We were the first revolution of the Enlightenment, and remain the only country to keep the same government for all these years. After viewing the course called "Cycles of American Political Thought," I can only agree with professor Joseph Kobylka's concluding thought: "If we - and our flexible philosophy of liberalism - are as exceptional as we think, perhaps this success will continue."