Morocco had the vast majority of a noisy and packed crowd at the Parc des Princes behind them and were simply too strong for the USA.
Soufiane Rahimi opened the scoring from the penalty spot before Ilias Akhomach and Hakimi added further goals in the second half, with another spot-kick, by Mehdi Maouhoub, wrapping up the win.
After topping their group ahead of Argentina, Morocco are looking like serious gold medal contenders and advance to a semi-final on Monday in Marseille against either Japan or Spain.
The Olympic men's football final will take place at the Parc des Princes next Friday, August 9.
The sizeable Moroccan community in France has turned out in big numbers over the last week to back their team, who came to the Games after winning last year's Under-23 Africa Cup of Nations.
They are a formidable side, captained by one of the world's best full-backs in Hakimi and with two livewire wingers in Akhomach and Abde Ezzalzouli either side of the prolific Rahimi in attack.
The United States never really looked likely to recover once Rahimi converted a penalty just before the half-hour mark after he had been fouled in the area by Nathan Harriel.
Rahimi, who plays in the United Arab Emirates and is one of Morocco's three overage players at the Olympics, is the tournament's top scorer with five goals in four games.
Miles Robinson did miss a good chance for the Americans just before the hour, but Morocco doubled their lead on 63 minutes.
Ezzalzouli produced a great piece of play on the left flank before picking out his fellow former Barcelona youngster Akhomach to finish at the near post.
Hakimi, playing on his Paris Saint-Germain home ground, then ran through to make it 3-0 with 20 minutes of the game remaining.
Substitute Maouhoub added another penalty in stoppage time after Harriel had been penalised for handball following a VAR review.
The remaining quarter-finals all take place later Friday with the pick of the ties in Bordeaux, where hosts France, coached by Thierry Henry, take on two-time gold medallists Argentina.
It will be the first meeting of the nations since Argentina players were recorded singing racist chants about their French counterparts as they celebrated winning the Copa America in mid-July.
FIFA announced that it would investigate the chants, which targeted France's star striker Kylian Mbappe among others and included racist and homophobic insults.
