Ghana started strongly and had the first sight of goal only for Florence Dadson to be pushed off her stride by a desperate last-gasp Julie Johnston challenge.
USA, however, went ahead on the 20-minute mark, albeit thanks to an element of luck. Direct from a corner, midfielder Morgan Brian powered an impressive header against the crossbar only for the ball to ricochet home off Ghana defender Linda Addai.
The second period was a different story as USA slowly turned the screws and gained the ascendency with a hat-trick from the impressive Hayes.
The Penn State University student profited from an inch-perfect Kealia Ohai cross soon after the interval to head home, before adding to her tally midway through the second half and then again in the second minute of injury time.
It was a vastly different start to the tournament compared to two years ago for the Stars and Stripes who, on that occasion, drew against Ghana in the opener before being eliminated by Nigeria at the quarter-final stage.
“I could not be happier after this match,” said USA coach Steve Swanson. “We are really happy with the result. Ghana is fast and athletic and played well. We have a great team and put in a good performance.”