I think love knows no nationalities :P Although I think nature in the (distant) past tended to put together people who looked very similar; now the world is a much smaller place, and people mix internationally a lot more.

Of course there is always a problem with cultural backgrounds, customs, religions and traditions though. And thats without even involving the parents! If couples are understanding and open minded to each others views/beliefs, it shouldnt be too much of a problem in my opinion.