Ahly players celebrate one of their goals against USGN (Photo: the club s official Facebook page)
The Red Devils, who were held to a surprise 1-1 draw in Niamey in the first leg of the competition's second preliminary round, looked to be cruising to an easy win after early goals from striker Mohamed Sherif and playmaker Magdi Afsha put them 2-0 up.
However, they were given a brief scare when Issoufou Hinsa narrowed the gap 10 minutes before halftime as USGN at times looked dangerous on the break.
But Ahly ran riot in the second half to stamp their authority, with goals from Afsha, Mahmoud Kahraba, Hussein El-Shahat and Hamdi Fathi giving them a comprehensive victory.
The Red Devils joined Cairo rivals Zamalek in the group stage as they eye a third consecutive Champions League title and a record-extending 11th crown.
Zamalek secured passage with a 5-0 aggregate victory over Kenya's Tusker on Friday.
Sherif missed a sitter after 35 seconds but made amends on nine minutes after some good work from full-back Akram Tawfik, who robbed an opponent with a neat sliding tackle on the right.
Tawfik then pulled the ball back into the area, where a poor defensive clearance bounced off Sherif, who pounced on the loose ball before his volley was spilled by keeper Saidu Hamisu into his own net.
Afsha doubled the lead on 17 minutes with a simple header into an empty net after being found by a delicate aerial ball from winger Mahmoud Kahraba, who was released by a superb threaded pass from left-back Ali Maaloul.
However, Ahly failed to kill off the game in the first half, with Sherif spurning another easy chance after being denied by Hamisu in a one-on-one situation, with the keeper then pulling off two fine saves in quick succession to smother headers from Walid Soliman and defender Badr Benoun.
Kahraba's follow-up effort agonisingly struck the bar and Ahly were taken aback when USGN struck against the run of play on 35 minutes, Hinsa's first-time right-foot effort nestling into the top corner after a cut-back from the lively Moumouni Diori found him unmarked just inside the area.
But any hopes USGN had of causing a huge upset were extinguished after the break as Ahly opened the floodgates.
Afsha was on target again in the 58th minute, beating a poorly constructed offside trap to chest the ball down, flummox his opponent with a nice piece of skill and drill a low shot into the bottom corner.
Substitute El-Shahat added the fourth six minutes later with a simple finish after wrong-footing Hamisu at the far post following a low cross from Kahraba.
Kahraba finally got on the scoresheet with a low shot from the edge of the area that went in off the post and substitute Hamdi Fathi completed the rout with a powerful drive one minute from time.
(For more sports news and updates, follow Ahram Online Sports on Twitter at @AO_Sports and on Facebook at AhramOnlineSports.)