I think Satoshi is an individual person. He writes with a consistent style. I doubt he's American, since he sometimes uses British spelling.
This thread is old. Since 2011 it has been created. But what interest me to respond to this. Is, this response of theymos explanation through contemplation that it assume that he doubt that Satoshi is from American and it writing is British writing, with this. It's shows that theymos have not seen Satoshi in person, but i assumed that theymos communicate with Satoshi even seat man to man and talk, that means no body will know if Satoshi is man or woman. This world is very big world.
That's interesting to know, and a very good observation from theymos, i think little details like this is what people should focus on to give a certain picture of who satoshi is. Again from what theymos pointed out about his style of writing, it could also mean either satoshi is one person and not a group of people using the name. Coming back to what the @op said about satoshi being a Japanese i don't know if the he has a source for that, anyone from any part of the world can take on any name as alias which does not directly connect to the persons origin.
Although this thread is old but i have just only come across it today, if the op is in doubt if satoshi is real then he is also in doubt if btc is real, satoshi decided to remain anonymous does not mean what he invented is not real or he/she is not real.