It is not clear whether there is a sensible definition of left and right other than "arbitrary convention set up by historical accident", but if there is, I suppose it would go along the lines of social status: the right are those who side with the elites and wish the present distribution of power preserved, the left are those who side with the underclasses and therefore wish to shift the balance towards more egalitarianism, from which would the lower status people profit (in terms of relative status increase, not necessarily materially).

I don't think that quite described the US, or Western Europe - the stereotypical redneck is low-status but on the right (same for ploucs here in France), and buying organic food seems to be more common with the rich, but is associated to the left.

A better description of the left/right gap may be that each represents a status ladder, and that people support the status ladder on which they have the best relative position. The details of what counts tend to vary with time and place, but on the left you tend to get status for being educated, open-minded, environmentally aware, original, etc., and on the right you tend to get status for being rich, responsible, having a family, being loyal to your country, etc.

At least, that angle of approach seems better than looking at policies; if you compare the policies of the French left and the American left, the policies might seem so different that they don't deserve the same label; but if you compare the kind of people who support either parties, the similarities are much more apparent.