Wedding ring customs: East vs. West?

Is there some sort of “dividing line” somewhere in Europe, where wedding rings move from the left hand to the right hand? Even in the U.S., many people who were married in the former USSR still wear their wedding rings on the right hand (although some switch it to the left hand as they adapt to American customs). I thought it was strictly a Soviet thing until a Romanian friend got married, and I noticed he wears his ring on the right hand, too. A Croatian friend says the Yugoslavs wear theirs on the left…

So what’s the background for this disparity? Is it a geographical division? A religious one, i.e. Catholic/Protestant vs. Eastern Orthodox? (Most of the former Soviets I know are Jewish, but they probably just adapted their wedding-ring custom to that most prevalent where they grew up, as Jews are wont to do; I don’t know any Eastern European Jews from outside the former USSR, so I can’t test the theory that way.) Any theological cites for the above? Is it related to other religious/cultural/historical splits?

Perhaps this is just adding to the confusion, but in Turkey when a couple get engaged they purchase their wedding rings and put them on their right hands. After their wedding ceremony the rings are moved to their left hands. I am assured by my (Turkish) wife that this has no religious significance.