Isn't Spanish the most learned foreign language by far in the States?
That said, Italian is pretty much one of the more useless languages in the world for anything outside of Italy, but I'm still quite happy with my choice:-)
They are more like the difference between, say, American and Jamaican English, than between two languages like English and French.
If you are learning Chinese as a foreign language, it almost certainly means you are learning Standard Mandarin (Beijingese?), since it's the lingua franca of the Chinese world, unless it specifically mentions Cantonese or Min Nan, etc.
I speak Mandarin and some Cantonese, Shaanxi, and Sichuan dialect, btw.