I understand what you mean, American doom metal often shows it's blues influences whereas European doom metal like Candlemass, Solstice, Scald etc do not. I also appreciate that about European doom metal.
For me the main reason I must go with America is due to it's death metal/deathgrind bands. Autopsy/Abscess, Necrophagia, Repulsion, Macabre, Impetigo, Dr Shrinker, Exhumed, Nekro Drunkz, Nunslaughter, Obituary, Nekrofilth, Meatshits, Incantation, Mortician, Blood Freak, Deicide, Possessed, Death, Deceased and so on.
I love doom, epic metal, USPM, trad, etc but I'll always be a deathgrinder at heart.