Does anyone know which country has the most bitcoins?
Finding out which country has the most Bitcoin's is not something that you can easily calculate it is very difficult as it involves geolocating the IP addresses. But with the way they get transferred it could be very different the next day. Also a lot of Bitcoin users are concerned about privacy and security and it may be difficult to acquire the actual geolocation data.

On the other hand.I can give you the numbers for Top five countries for Bitcoin downloads as of Today
1.US (1,207,661)
2.China (505,904)
3.Germany (270,043)
4.UK (236,523)
5.Russia (226,680)

Hope this helps