Excel: Create Pie chart from single column

1. Add new column (e.g. Count) and fill it with 1
   
2. Select your data (both columns) and create a Pivot Table: On the Insert tab click on the PivotTable | Pivot Table (you can create it on the same worksheet or on a new sheet)
   
3. On the PivotTable Filed List drag Country to Row Labels and Count to Values
   
4. Now select the pivot table data and create your pie chart as usual.
   

P.S. I use the pivot table for I update the data on a regular basis, then I just replace the "Country" data and refresh the pivot table.