In Stockholm, the other group leader, Switzerland, defeated Belarus 4-1 to achieve its best group record at the worlds, seven wins and no losses. The Swiss hope to medal for the first time since 1953, when they were third among three teams.
Julian Walker scored twice, and Roman Josi and Mathias Bieber once each.
Switzerland was followed by Canada and Sweden. Norway and the Czech Republic are vying for the last quarterfinal spot.
Slovakia's Branko Radivojevic was handed a free score after only 15 seconds when U.S. goaltender Ben Bishop turned the puck over, trying to reach a teammate with a pass.
Martin Bartek scored 3:44 in, and Rene Vydareny made it 3-0. Danny Kristo replied for the U.S. in the second period, and Marko Dano added a late empty-net goal.