Hah yes I was trying to think of a way of describing that - our inability to be rude to people, or speak up about something that seems wrong. That should certainly be added to the list.
I don't seem to find that hard at all. And I meet many strangers that are rude (not all of them foreigners).
It's true that brits hate complaining in restaurants. I don't think I've ever complained in a restaurant, despite my innate rudeness. But I find it very hard to keep my cool, when I've just listened to 30 minutes of hold music, and the person that picks up is an unhelpful numpty.
Or, maybe, our good manners?