What does this なのである do in this sentence?

Question

For full context, see here: https://www.docdroid.net/5vuuiCe/img-20170821-0002-new.pdf

The sentence in question (last line): 今、カラオケは単なる機械ではなく、日本が世界中に誇る文化なのである。

First, my attempt at translation: "Now, Karaoke is not (just) a mere machine and japan is a culture holding proud in the world."

I just translated the sentence as if なの wasn't present in the respective phrase because I don't know what to with it here. I also must say that I wonder wether my interpretation of the second part of this sentence ("Japan is...") is correct at all. It seems a bit far fetched to me to make Karaoke representative of the whole japanese culture xD At least this sentence sounds to me like it does so...^^ That said, maybe japanese people themselves think so. I don't know, I don't have that much insight into japanese people's heads :D

Answer 1

The なの is just a case of the "explanatory の" which adds a slight explanatory nuance to the sentence but doesn't directly affect the meaning much, so it's fine to leave it out in the translation.

However, I think you're interpreting the grammar of the rest of the sentence a little wrong. The subject (topic) of the second part of the sentence isn't Japan - it's still カラオケ, the same topic established in the first half of the sentence. So it can be rephrased as カラオケは日本が世界中に誇る文化なのである。

日本が世界中に誇る is a relative clause modifying 文化, so the whole thing means something like "Nowadays, karaoke is not a mere machine, but a culture for Japan to proudly display to the whole world."