Although I understand (and see value in) the heart of your argument I disagree with your description of media influence in Japan as being weak. Yes, I know you wrote "relatively weak" - in comparison with the US - but even so I disagree.
[WS:] Sorry, I hit that "send" button too soon. What I meant to say is "the media influence is generally weak, comparing to other societal influences" instead of the media influence in Japan is weak.
In other words, the argument was: "assuming constant level of media influence (which btw is relatively weak vis a vis some other social influences), their different effects in different societies can be explained by differences in the balancing effect of other societal variables. If the balancing effect is weak (e.g. in the US) the *net* effect of the media is stronger than in situations where that balancing effect is stronger (e.g. in Japan).
Wojtek