What was the air date in the U.S. for the episode that had 1.452 million Canadian viewers?
CREATE TABLE "table1_18424435_4" (
  "no" real,
  "num" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "canadian_air_date" text,
  "u_s_air_date" text,
  "production_code" real,
  "canadian_viewers_million" text
);
SELECT "u_s_air_date" FROM "table1_18424435_4" WHERE "canadian_viewers_million"='1.452';