I saw someone else make the same (IMO absurd) claim on HN yesterday and responded here: https://news.ycombinator.com/item?id=31335968

tldr; compare the US with China, Japan, India, or any other large country. The US is considerably less conservative than most—though not quite all—of the world.

The claim that the US is particularly conservative only really makes sense coming from an extremely Euro-centric worldview.