I used to think that too, but we accidentally ran an unplanned social experiment down here in Texas a couple of months ago when a freak weather event took out the entire state's power grid at a time when we needed it to keep from freezing to death. It lasted a week, and just about everything was out, everywhere. We didn't devolve into chaos and anarchy then - if we can collectively last a week without power in subzero temperatures, I have more hope for civilization than some.
Firstly, it started with an understanding that it would be extremely temporary. There wasn't much concern (at least among the people I know) that life couldn't go back to largely normal when things warmed up. There was damage, but in the scale of natural disasters, it was fairly tame.
Secondly, those temperatures aren't particularly dangerous. They're not pleasant, but it's not "oh shit, we're all going to die" territory. The death counts for that range from ~100-~200, including deaths from hypothermia, carbon monoxide poisoning from attempting to heat homes, and wrecks resulting from unsafe roads. That is a tragedy, but a relatively minor one in the scale of human tragedy. Hurricane Maria killed 3,000 people. Katrina killed 1,800. Crashes of large planes into uninhabited areas kill more people than that.
I don't mean to minimize the personal tragedy or hardships anyone faced, but "not having power during cold weather" isn't a terribly hard test of society's resilience. If you can manage to not freeze to death for a week, everything goes back to normal. Anarchy largely spawns from uncertainty; will they ever get the power back? Will I be able to eat? Will things get worse? If I do something drastic now, will I be able to save myself if/when things do get worse?
And they're not wrong. Without regular shipments of food into population centers the shelves will quickly empty out. Once that happens, people will start doing whatever might be required to feed their kids.
