A dating website (Manhunt.net) did some national breakouts for average penis sizes on the punters' profiles.
We all know what gay inches are so the actual numbers shouldn't surprise you.
As I've mentioned before, the Danes are expert cocksuckers and the Norwegians have bigger cocks.
Here in New Zealand, one of the most multicultural immigrant countries, it pretty much depends on your ethnic mix. I couldn't possibly generalise on penis sizes. It's definitely liquorice allsorts in the lollypop department here.