Methamphetamine is more popular in North America
Racemic amphetamine (in sulfate and other forms) is more popular in Europe
I dunno about other parts of the world, but stirfry is right, its all about the precursors and the local demands. Psuedoephedrine and ephedrine are still available in North America, whereas phenylpropylamine is now unavailable. However, phenylpropylamine is still easily acquired in Europe, and the market for regular amphetamine exists there.
From what I can tell, it is harder to get prescription amphetamines in Europe than it is in the United States, which would explain the existence of a market for illegally produced amphetamine in Europe.
If you ask me, you can blame the methamphetamine demand in the U.S. and Canada (of course coming from Mexico mostly now) on the pharm companies who have been pushing Adderall and Dexedrine on doctors and the general public since the 1950s, the work-until-you-die ethic the U.S. was founded on, and Hell's Angels.
Methamphetamine, the ultimate American drug.