Re:Turanian/Scandi/Baltic mix (Score 1)

That's a very oversimplistic explanation that fails to take into account, most obviously, the Florida death metal scene, Also worth mentioning are bands such as Sepultura (from Brazil) who helped found the genre in the mid 80's. If your theory were correct, we'd also expect a greater amount of higher-quality death metal from Russia and some of the cloudier/colder parts of the United States (Alaska and Washington-Oregon coast in particular) - places whose influence overall pales in comparison to the larger, more well-known scenes.