The Illini used a balanced scoring effort, led by 13 from sophomore small forward Malcolm Hill, to keep American at bay and ultimately pull away at the end for the 70-55 win.
The only other Illini in double figures was Rayvonte Rice, who finished with 10 points, 8 of which came on 8-8 shooting from the free throw line.
Both the Illini and American shot 5-12 from behind the arc, but Illinois made their first 18 free throws en route to a 19-21 mark from the stripe on the night compared to just 8-11 for the Eagles.
Illinois was able to disrupt American's deliberately slow Princeton offense for 19 turnovers and capitalized frequently for 24 points off of those turnovers. The Illini finished with 14 of their own turnovers, most of which came in the second half.
After a rough night on the boards against Miami, Illinois out-rebounded American 29-18 and did not allow a single offensive rebound by the Eagles.
No Illinois player spent more than 27 minutes on the floor (Egwu), as Groce continues to balance his starter and bench minutes to keep his team fresh late in the game.
Off the bench, Jaylon Tate and Maverick Morgan both had arguably their best outings of the year with Tate going for 8 points and four assists and Morgan scoring a career-high 8 points while grabbing 4 boards in just 11 minutes of time on the floor.
The Illini now head to Madison Square Garden to take on the Villanova Wildcats, who are red hot right now and hold an 8-0 record and wins over VCU and Michigan, in what might be their first real test of the season.