Just as the Chinese people in general, the so-called national language is also fractured. Standard Mandarin or Mandarin dialects? Putonghua, Guoyu or Huayu?
The confusion may lie in the fact that language and culture are separate:
"[T]here [isn't] a common 'Mandarin' identity based on language; rather, there are strong regional identities centered on individual dialects, because of the wide geographical distribution and cultural diversity of its speakers."
You could argue: Is there really even an English culture? Well, English speakers are a lot more alike than Chinese speakers. Still, we identify ourselves as citizens of our separate countries rather than as an English speaking group.
The feeling of being Chinese, on the other hand, is a different feeling. You are still Chinese no matter where you live, in China or overseas. It is larger than territorial boundaries.
Mandarin is a Portuguese word referring to Imperial Magistrates. As such it could be regarded as a language of officialdom. But that's where the simplicity ends.
I remember traveling around China and asking people what Mandarin was. No matter what tiny village I was in, everyone thought they were speaking the 'official' Mandarin.
Also, I have heard too that some Mainlanders admire softer sounding Mandarin of the Taiwanese to their harsher sounding Beijing style Mandarin. Somehow I doubt this but it may just be due to the influence of the softer Mandarin from movies.
If you are looking for the real Mandarin, well, good luck to you my friend. Just learn some kind of Mandarin. For now, Mandarin Chinese, whatever Mandarin you choose, remains the hot language to know if you want to communicate with the most Chinese, which is hovering around a whopping billion people these days.