Depends on what "know the US political spectrum of parties well" means, I guess. Those who know it really well are obviously well aware.

I myself know American Libertarianism, like you, only from debates with US libertarians on the web. They were present on an international Usenet newsgroup I frequented then, but for some strange reason, "outed" themselves only with Bush's election in 2000. (The result was a permanent war in a previously harmonic forum.) I met several of this type on other forums since (be them the Guardian's forums or other blogs).

However, in the run-up to the Iraq war, I discovered the www.antiwar.com site, run by anti-war libertarians - who I must admit impressed me, even as our economic views differed. Via reading an anti-war libertarian blog, later I even discovered the Mutualist school of libertarians, who put emphasis on their rejection of corporatism too - some agreement with leftists on economic matters, from a quite different ideological basis!

But I suspect most Europeans haven't even heard of American Libertarianism, not to speak of confronting its representatives.

_{*Lunatic*, n.
One whose delusions are out of fashion.}