That's why the term 'earth' is used. As you say, "countries on the soil" sounds dumb, but not necessarily wrong('cause you didn't say so
). So to make it sound better without altering its meaning, 'earth', is used. And (with regards to Jake)
There itself is apparent- 'earth', not 'Earth'. No caps dude... it's no particular planet. Not necessarily our Earth.
1. The interpretation of 'earth' as 'soil' is what makes it look dumb, really

2. Ok, that is a valid point, but still doesn't prove anything unless we can get hold of someone who knows Japanese. Also note the artical preceeding the word =p
Either way, I still think there is a good chance it
is our Earth if you fit in my theory there. Also, if I ever sit down to write a fanfic, I'll assume that it's totally up to me whether I make it based on Earth or not, and the player can exercise his imagination similarly because the idea is neither impossible nor ridiculous.