How can that be, if it's so incredibly difficult that Germany has not managed to do this?
The simple fact is that it has virtually nothing to do with any "difficulty" of finding a repository site, the problems are purely political, same as the US:
"The Government Accountability Office stated that the closure was for political, not technical or safety reasons.[6]" -- https://en.wikipedia.org/wiki/Yucca_Mountain_nuclear_waste_r...
Some German state governments even made this explicit, stating that they would not allow a repository to be designated until the German nuclear exit was finalized in their official coalition agreements.
Another nice little trick was changing the language to require the "best possible" site, rather than a suitable one. Sounds innocuous, but anyone with a bit of experience in algorithms know that in theory, this actually makes the task impossible, because how can you definitively prove that there isn't an even better site that you haven't looked at yet?
In practice it has made the process of finding a site incredibly lengthy, difficult and expensive. It doesn't help that the BASE, the Germany federal agency for nuclear waste has been completely taken over by the Green Party, so there is no interest in actually finding a site, and they spend almost their entire budget every year on spreading anti-nuclear propaganda.