JJ Hanrahan converted two tries and kicked a penalty for a 22-3 interval lead at the Stadionul National Arcul de Triumf in Bucharest.
A hand injury unfortunately forced Sean Dougall off the field in the 12th minute, only to be replaced by his new Munster team-mate Robin Copeland, who went to blindside with Tommy O'Donnell at openside.
Butler bagged his second try and the bonus point after only 52 minutes by scoring from the base of a scrum, and having notched up a penalty try thanks to Uruguayan ill-discipline, Billy Holland also touched down, finishing off a slick three-man move.
The South Americans exerted some late pressure in the Irish 22 before the table toppers, who face hosts Romania in their final game on Sunday, passed the half-century mark with a Paul Marshall try and a last-minute penalty from fellow replacement Ian Keatley.
IRB Nations Cup 2014
Romania v Emerging Ireland
Sunday June 22nd, 2014
Stadionul National Arcul de Triumf. KO 17:00
(all times are local to where the game is being played)