Not being real aware of the history around the Tolkien books, this is probably an ignorant statment. But to me the Hobbits being irish-y make some sense. As I read the books and the geographical descriptions I see the whole Middle earth thing as being set in some sort of ancient Great Britain type place. Gondor would be where Wales is, facing Mordor (London), strugling over control of England proper, the Nortern Dwarves being from Scotland and the Hobbits west of Gondor by the edge of the great western sea would put them about where Ireland is. The elves going off to the great land far west beyond the sea would be North America. The book talks about the men of the far south lands being dark skinned I believe. Think Spain which was controlled by the Moors from Africa in ancient days. The far east isn't really talked about, except that it's a place of deep evil and barbarism. Hello, France anyone?
Anyway, lower the sea level so that you can walk between Great Britain and mainland Europe, as it may have been in ancient times really, and you have a picture that almost fits the geography. At least in my mind anyway.