To work with mixed levels of detail from the Tableau geocoding, you'll need to use a dual axis map. I've made a quick example and attached the twbx (it's just random NUTS codes and State/Province values that I threw together in a table).
Essentially, you make a map with the NUTS (or State/Province geocoding data), then you drop another copy of Latitude(generated) onto Rows and use the second axis that shows up to map the other geographic level. To do that, you just replace the level of detail for that axis of the viz.
When just mapping with State/Province, you might also need a country field to help disambiguate.
state and nuts.twbx 36.5 KB