AC Milan edge Man City and Arsenal beat Man Utd in USA
Nasti lifted Milan ahead to stay in the 78th minute, the 20-year-old Italian striker taking a centering pass from Belgian right wing Alexis Saelemaekers and firing an inside right foot blast into the goal.
Several European sides are playing pre-season tune-ups in US venues ahead of next month's start of their league campaigns.
Norwegian striker Erling Haaland opened the scoring for Manchester City in the 19th minute, but Italian forward Colombo answered for AC Milan in the 30th and 34th minutes to lift the Italian side ahead 2-1 at half-time at Yankee Stadium.
City equalized in the 55th minute when Manchester hometown winger Micah Hamilton crossed the ball from the left side into the box.
English striker James McAtee headed the ball into the net, setting the stage for Nasti's decider.
At Los Angeles, Gabriel Martinelli scored for Arsenal in the 81st minute to give the Gunners a 2-1 victory over Manchester United in a friendly at SoFi Stadium.
Danish 21-year-old striker Rasmus Hojlund opened the scoring in the 10th minute for United.
Marcus Rashford lofted a clearing pass down the left wing and Hojlund took the ball and battled Arsenal defender Ayden Heaven into the box, where he got a step ahead and blasted a goal between the legs of Gunners goalkeeper Karl Hein.
Arsenal's Gabriel Jesus netted the equalizer in the 26th minute, the Brazilian tapping in a centering pass from point-blank range as the Red Devils appealed in vain for an offside call.
Martinelli, who helped Brazil to Tokyo Olympic gold, came in from the left side and flicked in a right-footed shot inside the near post to give Arsenal the winning margin.
Celtic rip Chelsea
Earlier, Japan's Kyogo Furuhashi and Denmark's Matt O'Riley scored first-half goals to power Celtic over Chelsea 4-1.
Luis Palma and Michael Johnston added second-half goals for the Glasgow side, while Christopher Nkunku averted a shutout for the Londoners with an 89th-minute penalty kick.
Celtic, who beat Man City 4-3 on Tuesday, dominated the match at the University of Notre Dame in South Bend, Indiana.
Celtic seized the lead in the 19th minute on O'Riley's left-footed blast from the right side of the box inside the far post.
An unguarded Furuhashi tapped in a left-footed shot in the 33rd minute from point-blank range off a centering pass from O'Riley to give the Scottish side a 2-0 advantage at half-time.
Honduran striker Palma boosted the lead in the 76th minute and Johnston netted the Hoops' final goal in the 79th.