There are many agricultural regions in North America where the growing season is long enough to allow pumpkin production well into autumn with no risk of frost.
Given that ...
There are many regions in North America where the growing season is long enough that you could grow pumpkins without risking frost damage.
Why is it that ...
Most pumpkin production in North America takes place in regions that do have a risk of frost damage?
Evaluate / Goal
If we're counterintuitively growing pumpkins in areas that risk frost damage (when other areas with longer growing seasons don't carry that risk), then there must be something really good about those areas with long, cold winters or something really bad about those areas with longer growing seasons.
Look for an answer helping us to justify why it's worth putting up with the frost risk in the regions where we do most of our pumpkin production (better land? easier distribution? etc.)