Write SQL query to solve given problem: What is the percentage of American players among all the players who have gotten in the Hall of Fame?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT CAST(COUNT(CASE WHEN T1.birthCountry = 'USA' THEN T1.playerID ELSE NULL END) AS REAL) * 100 / COUNT(T1.playerID) FROM Master AS T1 INNER JOIN HOF AS T2 ON T1.hofID = T2.hofID