I've just added country based stats for projects and for total BOINC.  New columns on the home page for Country By Team and Country By Member have the links to drill down into the stats by country

For Members, the individual projects are done straight, whatever country is on member record for that project is used, but for the boinc rollup purposes, the predominant country is used.  In other words, if a Member had none on 5 projects and United States on 7, United States is used as the total boinc country.  This is done simply to prevent splitting a member's stats among more than one country. 

I haven't decided whether to do that with teams on the overall BOINC level yet, but I probably will.  Right now teams are done straight, but the rub is that WCG doesn't have a way to set country so they all come in as None.  So I'll probably change it to predominant country for Teams also.