I always sort of took it as Kami-sama is both his name and job title.... much like taking God as both his name and job title, but...
Herms wrote:The call him "Kami, guardian of Earth".
I always took that more as them sort of like saying, 'It's Suushinchuu, the Four Star Ball' The idea being that God has many different names or things he's called. (In the dub, Karin also calls him 'The Big Guy' and Goku calls him 'Kami Guardian Sir.' at one point, iirc.)
Even still, I went back and took a look at Dragon Ball episode 125 dubbed and compared it to the subtitles (I've never watched original DB dubbed, only a good chunk of DBZ) and when he explains the origins of things, you're right, they do dub it as though his name is Kami rather than his position. In fact, the dialogue is honestly really close other than subbing in 'Guardian of Earth' for 'Kami-sama.'
It's not so much the part where he says 'My name is Kami, I'm the guardian of earth' but that when he explains how he took over, he doesn't refer to the previous 'Guardian of Earth' as Kami. I think if they would've done something to imply that the previous 'Guardian of Earth' was also called 'Kami' it would keep the way the Japanese one is set up more-or-less while also sort of explaining what Kami is.
I don't see what's inherently wrong with calling God the Guardian of Earth, though, even if it's sort of a really tame way to put it. Kami, God/Deity of the Earth maybe could've worked, but I think God by itself loses some of the meaning implied by Kami-sama. It loses some of the intent in that simplification, even if I do agree with you it's less confusing in a way... if only because is is simplified.
Herms wrote: When Dende takes over the role, in the dub they say he's the new guardian, not the new Kami.
My one question; In the original Japanese, do Popo and the rest refer to Dende as Dende or Kami-sama once he takes over? I've only ever read the US manga translations of the Buu portion, and I watched ancient fansubs of the Cell stuff back in the day so I honestly don't remember.
My guess is Popo probably calls him Kami-sama due to how that character acts but the others still call him Dende?