Best way to display users by location

I'm trying to find out which is the best way to display amount of users by location. In my application, you can create locations and sub-locations without limit. Then, you can assign users to each location. The thing here is that you can assign users in every level of your tree. For example, if you have Argentina > Buenos Aires, you can add users to Argentina and even to Buenos Aires.

Now, I need to represent in a chart how many users you have in each location, so I thought that a Pie could be a good idea in order to understand the percentage that each location has about the amount of users. The challenge is that you have a tree of locations, and you can assign users in every level.

I tried creating a graph in Highcharts but I think it's not too representative. If you take a look, South Park has 5 users and Brasil 40. The size of the piece of South Park it's similar to Brasil because of the hierarchy drawn, and that's not intuitive in a first sight.

Here's my example: http://jsfiddle.net/94y7z5ro/5/

Any ideas?