Tied at 27-all after their first leg, the Eagles and Uruguay clashed for a second time in seven days in Atlanta, with the winner guaranteeing their place at world rugby's showpiece occasion.
Despite the hosts going into the match as favourites they found it tough going in the first half, and with a Joaquin Prada try and eight points from Felipe Berchesi Uruguay built up a 13-3 lead at the break.
However the second half was one-way traffic, and with both Manoa and Dolan carrying the ball well the Eagles ran in four tries and 29 unanswered points to finish 32-13 winners, thereby booking a spot in Pool B alongside South Africa, Scotland and Samoa at England 2015.
Uruguay now enter a repechage process along with teams from Europe, Africa and Asia, while the USA will now look ahead to their summer test against Scotland in June.
Elsewhere there was a good trip to the Channel Islands for Alex Day, Tom Warren and Adam Parkins, who all saw action in Moseley's 39-8 comprehensive Championship win over Jersey. Meanwhile Reece Marshall was on the bench in Old Albanians' 25-28 National League One loss to Wharfedale, with Lewis Hall and Harry Betts both seeing action in Chinnor's home National League Two South reverse to London Irish Wild Geese.