Originally posted by GregT:
No doubt people will tell you differently and they'll talk about "Rutherford Dust" and the limestone of Chablis and the volcanic soils of southern Italy and the licorella of Priorat, but you can't taste those things.
What you can generalize about is the general climate, so you know if the wine is from a generally warm region or a cooler one, and you can generalize about the flavor profile due to the grapes. In Europe, as you know, they often specify the allowed grapes, so if something tastes like it's green and weedy and full of band aids, it might be an under-ripe Bordeaux, rather than say, something like Grenache from Ventoux.
People might argue that the "terroir" shows, and that you get a "sense of place", but if that were really true, you wouldn't have to limit yourself to particular grapes and even more, to particular yields, because hey, you should get all that famous terroir in every grape.
That is NOT to say that you can't distinguish one wine from another if you've had enough of the wine, and that the same grapes made into wine by the same winemaker but from another place will taste the same. They won't. But the winemaking, grape, and vintage trump pretty much everything else.
So GregT, if you tasted blindly you don't think you would be able to tell the difference between a Rutherford Cab and a Howell Mountain Cab? I think the OPs examples St emilion and Medoc are easier because of the high proportion of merlot in the St Emilion.