>anything else would be illegal

The US does not mandate snow tires at a national level, and in many places (even northern states where snow and ice are common) tire chains are illegal because they can damage the roads.

If you're going up steep hills covered in ice, winter tires or even studded tires are not going to work. You need chains. Then again, the best rally drivers are Scandinavian, so maybe you guys are just better drivers than we are :)

Western US. I can't comment on whether they should be required or not but they commonly are required in Utah, passes in the Sierras such as going up to Tahoe, and in the Cascades.

Seconded, grew up in far northern Minnesota and no-one uses snowchains there, though there is a preference for cars with high clearance (and some sand/skidboards in the trunk, usually). I guess I can see this if you're doing deep backwoods skiing, but that's an awfully niche pastime no? I've never heard of a ski resort that's inaccessible without snowchains.

>I've never heard of a ski resort that's inaccessible without snowchains.

Lots of them in the West. Little Cottonwood Canyon (at a minimum) in Utah. Tahoe from the Bay area (Donner Pass) under certain conditions http://www.dot.ca.gov/trafficops/trucks/chains.html. In a number of cases you can get exceptions for approved winter tires but it varies.