my cock-tour of Europe found that some British guys (particularly Scotsmen) can be well hung, Irish can go either way (long, Celtic pipe or 'Irish curse'), lots of big cocks in France and Italy, well, it's Italy...there are loads of big, fat cocks!
I gotta agree that all the French Canadians I've met were packing serious dick and in Holland they must put something in the water, 'cause I think it's a law that every Dutch dick must be big&fat.
But my vote for the nationality with the biggest would be Slavs-particularly Polish. The biggest cock I ever saw on a white dude belonged to a Polish guy with a shockingly fat kielbasa dick. Nice memory.