Why is the US so conservative?

[Mr. Morden]

I have sometimes wondered how much of it is simply the political system.  If the USA was a parliamentary democracy, in which it was actually straightforward for a party that wins a national election to actually pass some of its agenda, then universal health insurance probably would have passed some time in the 1960s or 70s, and it'd probably be uncontroversial today.  The American political system has so many veto points, that doing something big becomes very difficult.

And of course, the US has open primaries, with many (most?) members of Congress having to worry more about a primary challenge from their party's base than they do about being defeated by someone from another party.  That tends to lead to a very different cast of characters getting elected from what you would get in a "normal" democracy.