CREATE TABLE festival_detail (YEAR VARCHAR2, LOCATION VARCHAR2)

In which year are there festivals both inside the 'United States' and outside the 'United States'?
SELECT YEAR FROM festival_detail WHERE LOCATION = 'United States' INTERSECT SELECT YEAR FROM festival_detail WHERE LOCATION <> 'United States'
SELECT "YEAR" FROM "festival_detail" WHERE "LOCATION" = 'United States' INTERSECT SELECT "YEAR" FROM "festival_detail" WHERE "LOCATION" <> 'United States'