Write SQL query to solve given problem: Calculate the 2016 gap between the average revenue for Indian and American films.. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT AVG(CASE WHEN T3.COUNTry_name = 'United States of America' THEN T1.revenue END) - AVG(CASE WHEN T3.COUNTry_name = 'India' THEN T1.revenue END) AS CALCULATE FROM movie AS T1 INNER JOIN production_COUNTry AS T2 ON T1.movie_id = T2.movie_id INNER JOIN COUNTry AS T3 ON T2.COUNTry_id = T3.COUNTry_id WHERE CAST(STRFTIME('%Y', T1.release_date) AS INT) = 2016