I lived in the South for over a decade and the truth is that even trace amounts of snow really can cripple the roadways. We used to get a good blast of winter once or twice a year.
No idea on the differences between their asphalt composition and ours but there are some other reasons.
Tires being the main one. No one uses winter tires down there. All seasons are pretty much the best they do for changing driving conditions.
Also they just dont get the opportunity to drive on snow/ice very often so the experience factor is huge. Hard to learn on bad roads when you rarely see them.
And those mentioning infrastructure are bang on. Most jurisdictions dont have a bunch of snow removal equipment/sanders etc because its just not economical to do so. Its why they close schools etc...they just cannot do a lot to help the safety of school buses and similar transportation types. I remember one truly bad storm came through which stopped all traffic on major interstates never mind local roadways. People were trapped in their vehicles for up to 40 hours. Locals who had vehicles that could get through deep snow(snowmoblies/atv's/off road 4X4's etc)...banded together and took blankets, food and gas up and down I-40 to those in need. It was pretty neat to see actually.
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