South Africa walked over USA and qualified for the quarter finals with a 64-0 win in Wednesday, with Bryan Habana hitting a hat trick.
Despite losing the first match of the Pool B encounter against Japan, the springboks of South Africa have romped through the remainder of their matches and will face the loser in either Australia or Wales.
De Allende scored his first international try for South Africa to open the scoring, before the springboks were awarded a penalty try as USA struggled at the scrum.
It was a different South Africa in the second half, with Habana scoring almost immediately, while Bismarck Du Plessis and Francois Louw also crossed the line. After which Habana scored a brace of tries in two minutes to complete his hat trick.
Louw scored another to complete a brace, with Jesse Kriel adding his name to the score sheet, before Mvovo rounded off a dominating performance from the springboks of South Africa.