Kwesi Appiah's men were beaten 2-1 on Monday thanks to a late goal from John Brooks as Ghana lost arguably their most winnable game of the group.
With fixtures against Germany and Portugal to come, Gyan expressed Ghana's need to refocus for the fixture against Joachim Low's men.
The free-scoring German side put four past Portugal in their opener but the Al Ain striker said there was no time to dwell on the defeat.
"We have to improve in the remaining games and that’s the target," he said.
"The defeat to the US is painful but we do not have time to lament. We have to focus on our game against the Germans."
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