Why did you hand an argument off to me only to take it right back? You Indian giver
As for the Euro vs. American metal bands, I'm not sure where the whole "vs" issue comes from, as most of my "underground" (for lack of a better term, meaning non-MTV metalheads) metal friends, as well as myself, enjoy both.
If you're talking the MTV kids, then that's pretty easy, as most Euro-metal tends to write about fantasy, ethereal, or literary themes, which of course isn't going to fly with the "arrrrgh I'm so ANGRY" American nu-metal kids... though now it seems we're at the next evolution where the angry kids have hit the latter end of their manic-depressiveness and nu-metal has given way to the emocore "arrrgh I'm so EMOTIONAL" (witness BFMV and HIM)
As for good drop-D metal, don't forget most of Nevermore's work this decade