So, I've been following Mike Bostock's tutorial on creating a map.
To create the
-f GeoJSON \
-where "ADM0_A3 IN ('GBR', 'IRL')" \
Unable to open datasource 'ne_10m_admin_0_map_subunits.shp' with the following drivers.
A typical source of this error seems to be simply not being in the directory where you unzipped the file. Navigate to wherever you unzipped the downloaded files via terminal and run the command there.