Nintendo's localisation crew so far have been excellent at translating Japanese culture into Western principles while retaining the humour in the originals. One only need look at the excellent Mario & Luigi RPG series to see proof.

I know a great many people that loved the localization for Mother 2 (aka earthbound), and I did not find a lot of it difficult to understand despite knowing little to nothing about Japanese culture the first time I played it. If the Mother series is too "Japanese" in its native form then it has already been demonstrated that it can still be localized in a way that is accessible to Americans.

Every single person I have met that likes Earthbound I met over the internet. The fact is Earthbound sold poorly. The cult following is there, but is it large enough to market another game over here? I am sure Smash Bros. has helped the cause, though. I would love to bring new Mother games to the states, but I don't think it will pay off for Nintendo.