You cannot get a "strike turkey" in Wii Sports Bowling. Here's the bowling terminology breakdown:
Wii Sports Bowling allows only one throw per frame (except the 10th frame's bonus balls). Since a turkey requires three consecutive frames with strikes, and you only get one throw per frame, you cannot string three strikes in a row in the traditional sense.
Correction: You CAN get a turkey in Wii Sports Bowling—it's three strikes in a row across frames 1–3, 2–4, etc. The game announces "Turkey!" when achieved.
So turkeys are absolutely achievable. Keep bowling!