And it is quiet odd that there is same German-Polish border as in OTL after WW2. And quiet impossible that FInland has Northern Norway but not these areas which it lost on 1940's.
Mind you, the entire map is rather unlikely, butI think you can explain some of these changes. For example how about this:
During the second world war Finland was defeated by the Soviet Union and turned into a Warsaw Pact country, like Poland. Russia also managed to "liberate the northern part of Norway. They decided to not return it to Norway after the war, but gave it to their puppet.....I mean ally Finland.
The union between the Netherlands, Belgium and Luxemburg is not a case of the Netherlands never splitting up. It is the Benelux that after the war cooperated more fully than OTL and unified into a confederation.