Pariser Gipfel: Deutschland, Großbritannien, Italien, Polen, Spanien, die Niederlande und Dänemark – Warum diese Länder? (Kein Beschwerden, sondern nur um zu verstehen)

I saw that the countries that are going to attend the Paris Summit are: Germany, Britain, Italy, Poland, Spain, the Netherlands and Denmark.

For example, why Denmark? It’s because they are talking about Greenland, or it’s because they needed someone to represent the Nordics? Or some other reason.

And also, why the Netherlands, for example? I was expecting France, Italy, Germany, Poland and – maybe – Spain to be invited based on the country size and relevance, but wouldn’t have expected the Netherlands too. 

And for example, why not Romania, considering the size of the population and the strategic geographical position?

Again, I am not complaining, but I am just understanding the reason behind. Thank you!