What is the highest average rating for action movies made in the USA?
USA is a country
SELECT AVG(T2.rating) FROM movies AS T1 INNER JOIN u2base AS T2 ON T1.movieid = T2.movieid INNER JOIN movies2directors AS T3 ON T1.movieid = T3.movieid WHERE T1.country = 'USA' AND T3.genre = 'Action' GROUP BY T1.movieid ORDER BY AVG(T2.rating) DESC LIMIT 1