The USA needed to defeat Iceland to take top spot from them in the SheBelieves Cup tournament table and they did so comfortably.
However, the game had remained goalless until the last eight minutes of the first half, when Catarina Macario scored twice.
Mallory Pugh added a brace of her own after the hour mark and Kristie Mewis completed the scoring in a 5-0 win late on.
The result saw the US onto seven points, overhauling the six gained from Iceland from their back-to-back wins.
The Czech Republic had earlier played out a goalless draw with New Zealand to clinch third place in the table.