RED DEER, Alberta (AP) — Boston University goalie Drew  Commesso made 23 saves and the defending champion United States opened the world junior hockey championship with a 3-2 victory over Slovakia on Sunday night. Up 3-0 after two periods, the Americans held on after Martin Chromiak scored twice for Slovakia in the final period — the last with 2:33 remaining. Matthew Knies, Mackie Samoskevich and Landon Slaggert scored for the United States in the Group B game in Red Deer, Alberta. In Edmonton in Group A, No. 1 overall draft pick Owen Power had a hat trick to help Canada beat the Czech Republic 6-3. In the afternoon, Sweden beat Russia 6-3 in Group B in Red Deer, and Finland topped Germany 3-1 in Group A in Edmonton.