No, it is not genetic. Both Germany and Japan evolved into parliamentary democracies between 1870 and 1925. I have also seen it stated that the countries that had the best experience after the collapse of the Warsaw Pact all had a legitimate election (as viewed by the local population) between 1920 and 1939.
I thought Iraq had a chance, but that would have required keeping an elected government in place viewed as legitimate by the Iraqis for 30 to 40 years. See the experience of both South Korea and Taiwan, Single party dictatorships in 1960, by 1990 despite some uncomfortable and not entirely bloodless political upheaval both are multiparty democracies.
You wrote a thoughtful answer Fraxinus, and I don't disagree with any of it, except while those national histories might be taken show that success is genetic, they don't show that failure is not. Datum: all those nations have ethnically homogeneous populations.
Now take Iraq....Sunni and Shia, Arabs and Kurds, all involuntarily mashed together within boundaries drawn by some British foreign-office weenie who quite possibly had never crossed the Channel. Could there ever have been a stable democratic government there?