Why wasn't the suspected Chinese spy balloon shot down over Canada?

Critics say the U.S. and Canada had ample time to shoot down a suspected Chinese spy balloon as it drifted across North America. The alleged surveillance device initially approached North America near Alaska's Aleutian Islands on Jan 28. According to officials, it crossed into Canadian airspace on Jan. 30, travelling above the Northwest Territories, Alberta and Saskatchewan before re-entering the U.S. on Jan 31.