There's still several countries missing. Liechtenstein has been an sovereign country since the 19th century and Cyprus became independent in 1960. And depending on how you define Europe, one could argue that Turkey should be on this list since it has been independent since 1920.
Turkey is in Europe. Austria was reestablished as a sovereign state in 1955. From 1945 to 1955 it was under allied occupation and not an independent country.
Yes, it is. Not all of it, but part of it is. It's also in Asia, but historically it's been involved in major European affairs as well as being in European relation systems as well as competing in sports with Europeans. As well as that, part of it is geographically in Europe. I'll go for it's in Europe and Asia but saying it's not in Europe and a primarily Asian country isn't true.
It was already mentioned, but still: Austria didn't exist as a independent country in 1955. On the other hand, Free City of Triest did (existed as a independent territory from 1947 to 1954), so you should remove Austria and put Triest in to make it historically accurate.
I think think Trieste is missing it became a country in 1947 and lost its independence to Italy in 1954, if this is a quiz for 1950 I think it should be added.