It's a country founded on what you may call conservative ideas. I'm guessing that's really much of the explanation.
I also think it has something to do with how US society was created and even more with how Americans have idealized that process.
This, basically.
What really befuddles me isn't so much the fiscal conservatism of the US, it's the saliency of social/cultural matters and the continuous struggle over them.
Here in Greece, arguably the most socially conservative of European western democracies, abortion was legalized thirty years ago with little fuss, after being accepted practice for much longer, and nobody has ever talked about it again.
Gay people were never targeted for ridicule and condemnation by our (powerful) Orthodox church and its conservative political allies.
And while anti-immigrant sentiment is on the rise due to our economic hardships, there is nowhere near the venom and hate of people like Tom Tancredo and Steve King.
Same, but for
much different reasons. Unlike Europeans, I think the problem is not that America is too right-wing, but that Europe is too left-wing.