The Frenchman signed for the Red Devils under Louis van Gaal from Southampton, but failed to make the grade.
Schneiderlin eventually joined Everton, but he wishes he had left sooner.
"My regret is to not have played the 2016 Euros, and I'll have that regret all my life," Schneiderlin told Eurosport.
"Between 2014 and 2016, I'm in pretty much every national team squad, the manager had faith in me, he'd told me.
"The period of two to three months where I played less at Manchester United cost me my spot as an important player for the France national team. It hurt me.
"I told myself the most important was to play even if it was in a less exposed team. I maybe should have stayed at Manchester United and kept my head down. I would have certainly had a chance, but that's life."