Ironically, everyone involved with writing the "natural born" clause was born a British subject.
Considering their logic stems directly from their rule under the British, I don't think it's ironic at all. The States were so far away, and different (at least in their eyes) from the British, they British couldn't properly or effectively rule them. Thus it should be one of their own. And instead of some British snob coming over and taking over, they wanted to keep power in the family.
(Just a thought) America is so big, our pool for candiates is larger than whole countries (at least, technically speaking). Not to mention, we're so vast, you have people born live and die in America. Who always remain American. While Europeans are far far more likely to leave their countries (if only for holiday), work abroad, be more of a world citizen than wholly this or that. We could discuss the negatives, but Americans are more American than Welsh are Welsh (To speak crudely and simply).
I'm pretty humble.
*pets*