The Poles, who stunned Brazil 1-0 in the competition's opener, looked to be on course to another surprising victory when they took a 6th minute lead through Dawid Janczyk.

However, Adu and Co. produced a drubbing come back, as Danny Szetela (twice) and Josmier Altidore joined in the score sheet to conclude the huge score line.

USA became in charge of Group D on four points, while Poland are third on three points from two games.

The Ghanaian-born Adu became the first player ever to score a hat-trick in both the U-17 and U-20 FIFA World Cups, following his three goals past South Korea in the 2003 U-17 competition.

On the other hand, Brazil made amends for their opening day defeat to Poland with a narrow 3-2 win over Korea Republic, which included a brace from Chelsea target Alexandre 'Pato'.

Elsewhere, Brazil's South American rivals Argentina hammered Panama 6-0 in Group B, in which Atletico Madrid prodigy Sergio Aguero scored twice as well.