

I think the fundamental truth here is that any relationship requires conscious effort from both parties. One person alone can’t carry that weight. If your friend wants to salvage this relationship then I think they need to convince their partner to pursue individual therapy, and also they need to talk to a couples counselor together. Without professional help I think it’s going to be very difficult to shift the dynamic here. That being said, life is short, and you can waste years hoping that someone will change. Sometimes you have to make the hard choice to move on.
There are plenty of Americans who suffer from the exact same kind of social anxiety and lack of social confidence that you’re describing. If you’re only meeting or observing Americans who are traveling or living in Germany then your sample is skewed towards the kind of people who have the confidence and experience to travel internationally.
It sounds to me like you would benefit from talking to a therapist who could help you manage your social anxiety, but if you didn’t want to do that for whatever reason, I would try treating small talk as a skill that you’re trying to get better at. Set yourself a small daily goal - like having one chat about the weather with a cashier while you’re shopping. You can’t skip right to being an expert at small talk; you need to gain confidence and experience. I would like to say to you, in my experience, it’s easiest to talk about things you’re interested in or passionate about. Are there any groups or clubs that meet to engage in hobbies you like? A group like that can help you break through the awkwardness of not knowing what to talk about.
Personally, I think you sound like a thoughtful, interesting person, and I bet you’d be fun to talk to. Don’t be so hard on yourself, and remember that everyone has these feelings; it’s perfectly natural and not something to get down on yourself about. Sorry for writing a whole novel, but I hope this was helpful in some small way!