What is the average fastest lap time of the top 10 drivers in the 2006 United States Grand Prix?
top 10 refers to rank <11; AVG(fastestLapTime);
SELECT AVG(T1.fastestLapTime) FROM results AS T1 INNER JOIN races AS T2 on T1.raceId = T2.raceId WHERE T1.rank < 11 AND T2.year = 2006 AND T2.name = 'United States GrAND Prix'