national constituency; nationwide electoral district
Political term for a constituency that covers the entire nation, as opposed to a local district. Used in contexts such as proportional representation blocks or historical national elections.
Members of the House of Councillors under proportional representation are elected from a national constituency.
nationwide fame; being known across the country
Figurative extension of the political term: describes a person, product, or phenomenon that has achieved recognition throughout Japan. Often used in media and entertainment contexts.
He became a nationally known celebrity.
That product is popular nationwide.
選挙区 is a general term for an electoral district, which can be local or national. 全国区 is a specific type of electoral district covering the entire nation.
Compound of 全国 (zenkoku, 'the whole country') and 区 (ku, 'district, ward'). Originally a political term for a nationwide electoral district, later extended to mean nationwide fame or recognition.