Classical liberalism is, I think, little understood by the average American (or the average person from any country, for that matter). Misconceptions about what liberalism is abound. In American parlance, liberalism has become synonymous with democratic socialism. "Libertarianism" is roughly synonymous with classical liberalism in American parlance. American conservatives denounce liberalism because they reject democratic socialism. Many American liberals denounce libertarianism seeing it as nothing more than an adjunct wing of the Republican party, a front for Wall Street-style crony capitalism.
This is perhaps the most succinct summary of the ideas of classical liberalism I have encountered. It is the epilogue to a work of fiction titled Jonathan Gullible. I cannot speak for all libertarians, nor will I engage in an argument over who are the true heirs of classical liberalism. But I find the moral arguments of classical liberalism put forward in this document to be insuperable. I think it's important that people understand what classical liberalism really is - it is not a front for country-club Republicanism, it is not a front for a hidden, anti-values agenda. It is a principled commitment to the rights of all people based on the conviction that a world of people free to self-determine is the best of all worlds which can be realized in this physical universe and that a public policy of liberty is the most moral.
It's just a few hundred words... please read it.