The 66 points allowed by UMBC was a season low and 18 points below the team's defensive scoring average.
King led all scorers with 20 points, scoring 17 in the second half. De La Rosa added 18 points and five assists in 38 minutes of action.
American was led by Georgia transfer Troy Brewer, who scored 18 points, hitting 4 of 8 shots from behind the arc.
But UMBC had a dreadful stretch in the final 14 minutes of the first half and dug a 19-point deficit at intermission. The Retrievers could not take full advantage of a cold-shooting Eagles' start, as the visitors misfired on 11 of their first 12 shots from the floor. UMBC did build a 10-3 lead six minutes into the game, but converted on just two field goals in the final 14 minutes of the half and committed nine of ten first half turnovers in that stretch. American would outscore UMBC, 32-6, and take a commanding 35-16 lead into halftime.
American extended the lead to as many as 23 points at 50-27 with 10:49 remaining, but UMBC dug in defensively and was sparked by the starting backcourt duo of King and De La Rosa. When King stole the ball from American's Vlad Moldoveanu and drove downcourt for a layup and foul, UMBC had whittled the deficit to 56-47 with 1:28 to play. But King missed the ensuing free throw and Eagle post Stephen Lumpkins converted a three-point play inside 15 seconds later to snuff out the hopes of a Retriever rally.
After being outscored, 18-3 on second chance points by Towson on Saturday, UMBC was oupointed, 10-3, in the same category against the Eagles. American had a 38-27 rebounding edge and only three Retrievers managed a single offensive rebound apiece.
UMBC travels to Morgan State for a 4:00 p.m. tilt on Saturday, Dec. 18.