Write SQL query to solve given problem: Calculate the percentage of the nominees who were born in USA.. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT CAST(SUM(CASE WHEN T1.birth_country = 'USA' THEN 1 ELSE 0 END) AS REAL) * 100 / COUNT(*) FROM Person AS T1 INNER JOIN Award AS T2 ON T1.name = T2.person WHERE T2.result = 'Nominee';