This post has two parts, the whiny Americentric part, and the more rational part.
WHINY AMERICENTRISM: Holy cow, is it ever strange walking around at the Bergkirchweih, or for that matter in any crowd in Franconia. You are, in the eyes and minds of everyone around you, a rock to avoided or elbowed aside. A complicated rock, because you are moving, but nonetheless a landscape feature without feelings or goals of your own.

So, suppose for example some lady is trying to push a stroller through a narrow space, holding a toddler in one hand and a backpack in the other. You, at the other end of the narrow space, stop and smile, indicating that she should come ahead (it's too narrow to pass each other.) Immediately the people behind will brush past, not even trying to avoid pushing you, and will walk through the narrow space. This will continue basically indefinitely. As far as they are concerned, unless they know the lady, or you, personally, you can just go screw.
Same thing at the grocery (yes,
I used the Euro this time). If you leave a space, the person behind you will cut around you to take the space, even if you clearly trying to let someone past. After a while, I switched, and starting giving people the forearm myself. A little old lady tried to push past me, and I rammed her cart right into the bean cans. She didn't get mad, didn't say a thing.
It's like a pick-up basketball game, same rules. A really egregious foul would get you into a fight. But you don't call incidental contact, and "incidental" means no ambulance. And, in a pick-up basketball game, you would never tell your opponent, "you go ahead, I'll wait;" and then smile at them. But it is annoying to someone of Southern (southern US, not southern German) sensibilities. We tend to negotiate space, smile at each other, and even talk and laugh. It is considered actively rude here in Franconia to talk to someone unless you have been introduced. Asking for help is okay; that's the exception. But looking someone in the eye, smiling, talking: all way out of bounds.
RATIONAL PART: Fact is, I am the one being rude. These are the rules here; I can accept that, or leave. Trying to insist on my parochial conception of "manners" is actually pretty bizarre.
Look, the fact is that as long as everyone has the SAME expectations, and same conceptions of manners, it's all good. The problem is when you get a mix. Several times, I have caused minor bike-bump accidents when I slowed down to let someone in. No one, including the person being let in, expects that. And the fact is that they don't NEED to be let in. They are very skillful bike riders, and if the person merging just pushes in, the others accommodate skillfully and rapidly, though minimally. It goes much faster than the American system, where letting someone in is a courtesy, one that can be actively withheld. It would be rude here to EITHER (1) swerve to deny another bike a space, obviously and on purpose, OR (2) to slow down to let them in, making everyone else have to swerve unexpectedly. Think of the times in the US you have seen one car wave another car in, or obviously swerve to KEEP them from getting in. Neither of those things would happen here. And, when I think about it, I'm not sure but that this is a better system. (Though, they really should let the lady with the stroller, the kid, and the backpack through. I'm going to throw somebody through a fence if that happens again.)
So, *I* am the one being the jerk. When I think it over, I can see that that is clearly true. But it does take
some getting used to, as others have noted.
Another example, from the US: Consider the "Pittsburgh Left Turn."
Read this, for just a second, and then come back. Okay, got it?
Now, if a lot of people NOT from Pittsburgh are driving in Pittsburgh, there will be accidents. Who is being the jerk? Well, no one. The problem is a mix of cultures, and the consequent divergence of expectations and norms.
(I should acknowledge that NeanderBill told me about the Pittsburgh Left. And he knows from Left, I tell you).