To display in pie-charts, field values should be 12 or below for effective analysis.
if we put all the countries in one pie chart it would be like below
for your requirement it would be best if you create a dashboard as shown below.
I created three sheets...
Sheet 1 is a Filled map chart color coded with Sales
Sheet 2 is Bar Chart with City wise Sales
Sheet 3 is Pie Chart with Categories wise Sales
Drag them into canvas and make a dashboard in depicted fashion
provide action filters for Country to City Charts & City to Category Charts
This would be more meaningful visualization
For more information Please find the attached workbook below
Drilldown.twbx 7.0 MB