DVDs have a double-whammy. First, there's the 525/NTSC (American) vs. 625/PAL (British/European) video format issue. Second, they have a region coding system which was intended to restrict viewing to certain countries, supposedly allowing the distributors to release DVD's at different times in different parts of the world.
Fortunately, the audio CD standard pre-dates all this nonsense and also has the same digital audio format the world over.