> so you can call anything a nation state as long as that thing issues a passport i guess?
What? No - you just gave the argument against that!
> are united also by factors which define a nation, such as language or common descent
This means the UK isn't a nation state - we have four nations in the UK, with different cultures, descents, and in some areas even languages.
It also means that the US is not a nation state - the people there have very distinct descents. Today Americans literally still say they're 'Italian' rather than 'American'. Many Americans don't speak English. The US literally describes tribal lands as 'dependent nations', so it isn't one nation even by their own federal definition.
Examples of nation states are places like Iceland and Portugal. These are the major military players that the original comment was trying to refer to.