Matt Yglesias points to an OKCupid survey which shows that in the United States there tends to be a rather coherent block of social & economic conservatives within the Republican party, while the Democrats are a coalition between those who emphasize social issues and those who emphasize economic issues. Social liberals are often found in the upper socioeconomic strata and look positively upon globalization and free trade. Economic liberals, in the American sense, are not necessarily social liberals, as is well known in the case of black Americans who tend to support government programs but are more socially moderate-to-conservative. Combined with the consistent pattern of conservatives outnumbering liberals it would naturally lead one to believe that this is a nation where the Right is eternally ascendant.
And it is certainly true that compared to European nations the United States is conservative on many social and economic metrics.* But is the arc of American history toward a conservative or liberal direction? In other words, what is the probability that there would be a blanket ban on abortion in the United States in one generation? What about the maintenance of federal laws which ban recognition of same sex marriages? Which the proportion of national GDP which consists of government spending?
For all the talk about American exceptionalism the arc of history seems to be moving to the Left, broadly speaking. Despite the reality that the American Left seems weaker in numbers and less coherent a movement than the Right, conservatives have been waging a rearguard battle by and large. The macrohistorical trends are simply not born out by the strength of numbers that conservatives have at any given moment. One might infer from this that there are strong sociocultural dynamics and institutional biases which nudge Western liberal democracies in a Left direction, with the rate of change modulated by contemporary political configurations. And yet perhaps we are too Whiggish, human history has been characterized by secular trends being nested within broader cyclical patterns.
* This has been to be qualified, as many European governments have more restrictive abortion rights regimes, and racial nationalist parties gain more traction in most of Europe than they ever would in the United States.