Since the start of the Connections, there has always been a soft rule against adding connections that solely consist of sites in one country.
This has been done to avoid uncontrollable growth of the number of connections (as sites that lie close to each other will have many things in common). But still, a few have been added:
In former GDR is a good example I think.
To make it clearer when I am inclined to add a "one country connection" and when not, the recent discussion about various River Basins can serve as an example. "International relevance" would be the key.
- We do have Volga (Russia only already), and I'd be happy to include a Yangtze (China only) connection. These are major river systems on a global scale and everybody will have heard of them.
- The Weser, on the other hand, is relevant to Germany only.
Another example: if we could think of a NL-only connection covering sites relevant to Rembrandt, I would include it. But I would not include one that links 3 WHS to a Dutch prime minister from the 1970s.
I will double-check the ones we already have.