The idea is to make it as practical as possible for the user:
- I would use the long click for something else, maybe a small menu about the continent/country
- The edit button at the top should enable/disable the checkboxes (but it should be aligned on the right)
- Issue: When enabling a country, then the whole continent it belongs to, and then disabling the continent again, there is no undetermined state anymore, the box is unchecked
