Issue with join duplicating data

So I have a data set with data for different countries. The data is aggregated from >1000 different sources.

I am trying to make a dashboard in which the sources can be listed in the dashboard and filtered when a country/region in a map is clicked.

All that is fine when there is only one source for each country. When there are multiple, the join results in duplicated data. This then causes errors in the aggregate measurements for the world and for regions (I can get around it for countries by taking the average).

I think the solution to this may be data blending, but I can't figure out how to get that to work.

I have tried a number of work-arounds, but none have been able to make country, region, and world aggregates work.

See the attached example workbook. Ignore the data, but United States and Greenland demonstrate the problem pretty well.

The only other option I can think of is to put all sources for a country in one row and not duplicate, but I don't know if formatting (line break between references) would carry over into Tableau.

I really appreciate any help you can give me here.