http://www.americasrugbynews.com/2015/09/13/foreign-born-players-rwc-2015/
Contrary to popular belief about some countries raiding others for talent, if this article is to believed, NZL and AUS are the primary exporters of talent at RWC 2015. I added one in to the total for Wales to cover the late call up of Gareth Anscombe.
"Exporting" countries
New Zealand, 40 players born in NZ that represented a Nation other than NZ at RWC 2015
Australia, 17
England, 15
South Africa, 15
Fiji, 6
Tonga, 6
Argentina, 5
Zimbabwe, 4
Ireland, 2
Spain, 2
Algeria, 1
American Samoa, 1
Belgium, 1
Burkina Faso, 1
Cote d’Ivoire, 1
DR Congo, 1
Georgia, 1
Israel, 1
Netherlands, 1
Nigeria, 1
Papua New Guinea, 1
Russia, 1
Saudi Arabia, 1
Scotland, 1
USA, 1
Wales, 1
Who have been the receiving countries:
Samoa, 13
Wales, 13
Tonga, 12
Japan, 11
Scotland, 11
France, 10
Australia, 9
Italy, 9
USA, 9
Canada, 6
Ireland, 5
New Zealand, 5
Romania, 4
England, 3
Fiji, 3
Namibia, 2
Georgia, 1
South Africa, 1
Uruguay, 1
Argentina, 0
Where are the Aussie Born "Exports" playing and on what grounds?
Wales, 1 - James King (residency 1993)
Tonga, 3 - Jack Ram, Steve Mafi, Tevita Mailau (all Parents)
Japan, 1 - Craig Wing (residency 2013)
New Zealand, 2 - Ben Franks, Tawera Kerr-Barlow (all Parents)
Italy, 2 - Joshua Furno (parent), Luke McLean (Grandparent)
USA, 4 - Al McFarland (residency 2015), Greg Peterson (Grandparent), Hayden Smith (residency 2008), Matt Trouville (residency 2014)
England, 1 - Billy Vunipola (residency 1995)
Fiji, 2 - Ben Volavola, Campese Ma’afu (all Parents)
Canada, 1 - James Pritchard (Grandparent)
Edit: James Pritchard added as per @RugbySkier