Alright, let's look at this a little deeper. The German teens have self-control, but American GI's don't. Does that mean that the Germans are genetically superior? Or does it mean that we, as Americans, have had self-control bred out of us, by an overbearing nanny-state, that decides what we may or may not put into our bodies, without a prescription? (state permission to ingest drugs that lobbyists clients are profiting from)
Eventually, the only, "limits", a person may know, are the ones legally imposed. Once those limits are lifted, that same person does have trouble discerning for himself where and when to stop.
That is part of what I was saying. The Germans have some self control in these areas as they grow up drinking wine and beer everyday. It is a part of their culture. We put a stigma or an aura of mystical magic around drinking.
We can not wait until the magic number 21 to get stupid blind drunk and show everyone how tough we are. It was part of the teen culture when I grew up.
To sneak some beers and roll around getting silly was a part of growing up.
Not so much in Europe.