Having lived in a city that doesn't clear most of their side streets when it snows (and does a pretty shoddy job of clearing the major thoroughfares, too), I'm not sure cars are particularly practical in harsh winter conditions, either.

Cold is a problem, but with the right gear, you can stay plenty warm down to 0F. I'm sure we could use microcars (https://microlino-car.com/en/microlino) or some other variation on enclosed ebikes to share bicycle infrastructure safely with folks who can't use bikes when it's truly cold out. The same strategy could work for extreme heat and humidity.

The real problem is safety, rooted in snow clearing and ice buildup. Many cities refuse to maintain bike infrastructure at all during the winter, allowing snow and debris to build up on bike paths and lanes between Nov and April. This means that even when roads are clear, bikes aren't able to use dedicated bike infrastructure during much of the winter months, forcing bikes into car lanes. And my experience as a bike in those circumstances tells me that many drivers are NOT accommodating to bikes in that situation. This problem exists year-round, but snowy conditions make it even more obvious that cars, pedestrians, and bicycles don't mix well in our cities.

Nobody needs to drive around massive SUVs, pickup trucks, and semis around dense downtowns. Many European cities get by with cargo bicycles and minitrucks (https://minitrucks.net/pages/direct-import-mini-trucks) to move 99% of packages and large items in city centres. The USA needs to keep large vehicles out of dense urban centres and turn as much infrastructure as possible over to pedestrians, public transit, bicycles... and microcars and mini trucks for the niche situations where those other modes of transportation won't work.