Take for instance you are a German
Why does that sound like this thread is aimed at me?
No, it's not absurd. Cross-cultural marriages happen, and many of them work well. Of course they have their own issues to deal with, for example those questions you mentioned. But their cultural difference can also be a resource to draw strength and inspiration from.
A woman that was my best friend in childhood days (we grew up next door to each other) is now married to a man from Ghana whom she met during her student exchange in Paris. I haven't talked to her in many years, but my parents still talk to her parents, and from the sound of it they are a happy family with two racially mixed kids.
They still live in France together.
Also many years ago I participated in a volunteer exchange program in Zimbabwe. Pretty dang crazy country. But while being there I had a crush on one of the local guys. He was very educated and "western" (priviledged wealthy family background), and he was a psychology student like myself. I enjoyed talking to him very much. Also, he was hot.
I hope life will always treat him kind.
But I had a boyfriend waiting for me back home whom I also loved very much and wanted to be loyal to. Anyway, the idea of falling in love with someone from a different culture is not absurd. There's two opposite force is everyone's heart, one side is about finding and clinging to familiar things that we know and understand and can predict to give us a sense of belonging and safety. The other side craves excitement and exotic things that are different from what we know and give us a sense of adventure and challenge. Any relationship must find a balance between those two needs.
If you get married to your highschool sweatheart that grew up in your part of town you may be feel save and home easily, but you may also at some point start wondering if that's all life has for you, and where is the excitement and the adventure?
If you marry someone from a different continent and a different culture it's the opposite. It's all exciting and sexy, but in time the cultural differences may cause discord or misunderstandings and each side may long for an environment that is more familiar with them.
So you always gotta balance the need for similarity (safety) and the need for new-ness (excitement).
And any marriage is a challenge anyway. ;-)