DRESDEN, Germany — For 45 minutes, the Americans were sloppy and slow, looking very much like the inconsistent bunch whose road to Germany was marked by bumps and potholes.

Once they took the field for the second half, though, the Americans played with the confidence, creativity and touch around the goal that won them two World Cups and made them the world’s dominant team for much of the last two decades.

“We believe we can win this tournament,” Abby Wambach said.

Lauren Cheney, making her first start since March, and Rachel Buehler scored in an offensive burst as the Americans beat a young but scrappy North Korea 2-0 on Tuesday. The victory puts the Americans atop Group C going into Saturday’s game against Colombia.

If the U.S. wins that game and Sweden beats or ties North Korea, the U.S. will be on to the quarterfinals. The Swedes defeated Colombia 1-0 on Tuesday in the other group match. The U.S. wraps up group play July 6 against Sweden.