Why is it that here in the Northeast US seemingly no one preheats their
automobile engine before start-up in very cold temperatures? Is the long-term
damage the same for both autos and aircraft engines? If so, why do you
suppose auto owners don't typically do this? Is it because that most auto
owners do not keep their cars very long?

--
Peter

Lycoming says you can start without preheat down in the teens if you
use multiviscosity oil. As others have said, one of the biggest
differences from auto use is that aero engines are often flown less
frequently so there's less oil hanging around at startup. On the
other hand, that's true even in warm weather, though warm oil will be
redistributed more quickly.

I doubt that you did any harm. Convert all the degrees to Kelvin
temps and be comforted :-)