I've come to think the American norm is something of a self-fulfilling prophecy. Bedsharing becomes dangerous mostly when the parents fall asleep intoxicated. You might have noticed that you're much more likely to wake up with your arm partially numb if you pass out drunk than if you go to sleep sober. But because bed sharing is discouraged, it's mostly less responsible parents who do it, which creates a stronger apparent correlation with infant suffocation.
I think this might have been the case early on. Now it seems the reality is more nuanced.
Now the default discourages bedsharing, but we know and can witness personally the many positive effects. The warning causes us to be more conscientious about doing it if we choose to, and for those who default to obeisance they are in their minds making the responsible choice.
Because of the social stigma, those who do bedsharing responsibly are not being accurately reflected in the data, causing only those careless enough to admit it to be captured.
Pretty sure Americans drink less than most Europeans.
And not just alcohol. America is highly medicated. Someone who takes sleeping pills for example is unlikely to be subconsciously aware of their surroundings.