CREATE TABLE table_21634403_2 (us_viewers__millions_ VARCHAR2, directed_by VARCHAR2)

How many U.S. viewers watched the episode directed by Frank Waldeck?
SELECT us_viewers__millions_ FROM table_21634403_2 WHERE directed_by = "Frank Waldeck"
SELECT "us_viewers__millions_" FROM "table_21634403_2" WHERE "Frank Waldeck" = "directed_by"