I've experienced no over-the-top damage modelling in Nascar 3 which I
personally can complain about.
How fast were you travelling during this collision? Remember that at speed,
even the slightest knock is enough to cause at least some damage - even if
it's just a panel beating. Tearing off a bumper isn't the most difficult of
accomplishments either. They're hardly the strongest and most reliable part
of a car.
It's possible that in this particular race you were just unlucky. The game
could have made a calculation mistake, or perhaps there is a bug (just not a
very big, or important one).
If you'd like to reduce the amount of damage your car can receive, remember
that you can switch the damage modelling to Arcade. That will allow you to
nudge and grudge as much as you like with the least damage possible.
Personally, I love being aware that one slip-up can ruin an entire race.
Best regards,
The Phoenix