Yes, cultural gaps in middle size groups are probably the toughest.
The group is too large for you to simply wait to speak and change the topic to something that makes you stand out as interesting and lead. So you must speak on the current topic if you are going to speak.
But you may be in the position of having nothing to say about that topic: especially if it's something cultural or local and you come from outside.
Yet the group is not large enough, too small, to agree, for the sake of convenience, to simply give an interesting speaker the platform and behave like an audience. (Whose attention a good speaker can then grab and hold.)