The biggest advantage an M1 would have is the tech inside. If it was sent back the absolute best use for it would be to strip it down and reverse engineer everything in it. Jumping 50 years in circuitry and engine design would make a lot of difference.

If you actually deployed it, the first trench it went over would likely get a rock caught in its treads, they’d derail, and it’d get pounded with artillery for the hour it takes to fix the treads.