Anyway, aside from those two cities the main reason people don't cycle has been shown time and time again to be lack of infrastructure, not the weather. Just look at other places with the same climate as The Netherlands, or Bergen. Clearly the common factor isn't the weather.
It's also a much bigger factor than people imagine. I've lived in Iceland which often has these sort of glassy ice conditions an -5 °C, and I'd much prefer it to otherwise equivalent weather at 20 °C somewhere else.
The cold allows you to push harder without being sweaty, and I've found that in mixed terrain cycling on ice with studded tires is a lot safer than on no ice. It's a lot easier to slip on loose gravel than it is to slip on ice when your tires have a dozen nails sticking into the ice.
Edit: The parent pointed out that Minneapolis was one of the top cycling cities in the US with around 4-5% of trips made by bike (compared to Europe's 2% average, 10% for Austria & Germany, and >20% for the Netherlands and Denmark). Then deleted the comment for some reason.
Some Minnesotans fly to Arizona every winter to avoid the icy streets here. They are called "snowbirds" locally. I used to think that was an extravagant lifestyle, but when my dad was not quite seventy-two years old, in April in Minnesota, he slipped on ice while on a trip to the local grocery store and then was paralyzed (quadriplegic) for the last six years of life, unable to care for himself at all. Since then, I have taken icy streets much more seriously. I still bike a lot, and I still stay in Minnesota during the winter, but I realize now that walking or biking on ice can have catastrophic consequences.
I agree with the idea that designing a city to be more bike-friendly increases bike trips. I enjoy where I live now because my city has an extensive set of city bike trails (which in the winter are sometimes used by Nordic skiers) that connect to regional trails (former railroad lines) that extend all over our metropolitan area. But I watch out for ice for half of each year.