He joined the 36-time Italian champion for the 2020-21 season, had his following season cut short by a broken foot, then was loaned to Leeds United last January and couldn't help the English club avoid relegation.
"Coming back to Juventus wasn't easy," the 25-year-old midfielder said Thursday during a news conference at U.S. national team camp in St. Louis. "I left the club at a time of crisis, I guess you could say.
"And so coming back I felt like I started back at square zero, but that is a challenge I'm always up for, a challenge that I think I needed at this time in my career to kind of prove to people that I still have it."
Juventus was penalized 10 points in the standings last season for financial violations, causing it to miss out on this season's Champions League, then was banned from all UEFA competitions because of the improprieties. A team that won its ninth straight title in 2019-20 hasn't won another since.
McKennie has gotten used to switching teams, saying his nomadic upbringing was preparation -- his father served in the U.S. Air Force.
"I could make friends with the rock if I needed to," McKennie said. "And that's just because everywhere we moved, I had to make new friends. I had to adapt to new cultures, adapt to new situations and new environments. And so, obviously, moving around teams and moving to different countries, starting at a young age definitely benefits to my situation now."
Weah, a son of Liberian president and former FIFA Player of the Year George Weah, joined Juventus from Lille in July. Both started all four matches for the U.S. at last year's World Cup and while the 23-year-old Weah is a winger for the Americans and McKennie is a central midfielder, both have been playing out of position in Italy.
"You're looking at starting right wingback and backup right wingback right now," McKennie said with a wide grin as he started to laugh. "With us being able to play so many different positions and being able to adapt to so many situations and roles, I think it's a good quality to have. I don't think that we really stress that much about it."
Weah first was shifted to wingback by Lille last November because of injuries.
"It was still very much a learning phase for me," he said. "I think Juve was more of a defensive team last year and they definitely brought me in to play more of an attacking role, coming out the back, which is something I love doing, getting runs in behind the defense, just applying pressure."
"I understand how he plays. He understands how I play. So our chemistry is really good," Weah said of McKennie. "Now that we're on the same team, training every day is just going to make it even better.
"Outside of the field, I can be a little bit little bit too much for Tim at some times," McKennie quipped. "But on the field ... we have a good understanding of each other and coming into camp, it's good to have a travel partner."
Saturday's match against Uzbekistan will be the first match for Gregg Berhalter in his second term as coach. Berhalter led the team to the second round of last year's World Cup before a 3-1 loss to the Netherlands, then was replaced by interim coaches from January through July.
"It's just picking up where we left off," McKennie said.