I'm completely talking out of my ass here but I feel like how relatively uncommon meth is in EU compared to US has to do with ingredients being a lot harder to get in the EU area. Crystal is common in the US while in EU that is extremely rare, the meth on eu market is usually powder or rock.

I'm assuming most of crystal meth in the US comes from mexico and they don't bother to ship that much of it overseas as stuff like cocaine has higher profits and a bigger market.