We've not been given a solid reason for the delay, but a rumour has emerged which seems plausible. According to Nintendo Nation, a GAME customer was told by a store manager that the game was recalled because it doesn't feature UK English spellings. Instead, the dictionary in the game uses US English — which means "Color" and not "Colour", and so on.
This story is supported by the fact that the PC version of the game — which is available in Europe — also contains US spellings while omitting some UK English words.
Does this sound like a reasonable explanation to you? If so, why didn't Nintendo just patch the game after release? Drop a comment to share your opinion.