It's always all seasons tyres from rental companies. I went to Yosemite in April and there were announcements on the radio that chain control was in effect, we drove into the Valley and decided not to get into the park. We met some ladies and they said it looked fine inside and said we should have a try.

Got to the park and asked the rangers and they said, "There's no chain control here and you have an AWD". We paid and got in.

As others said, black ice is the real issue as it's dangerous and you can't see it. When the road condition is like this, use big roads (preferably motorways). Snow tyres are actually great to drive on ice rather than snow. We live in Denmark and we have summer tyres on our EV and we haven't changed it to winter tyres as we have more water than snow/ice with fridge temperature so we think it's not optimal for winter tyres.

I went to Banff in May and rented a car at Avis YYC. Got a Chrysler 300 and asked them if it's ok to take it up to the mountains and they said no problem. I drove it on snow and all the way to Jasper and had 0 issue. The thing is, if there is a snowstorm up there the roads will be closed, if it is normal, the major roads will be plowed anyway so it really doesn't matter what tyres you have.

The worst experience we had with rental cars and winter condition was actually in NM, when we drove our car in snowstorm and the windscreen heating system was broken so it constantly steamed up. Then the tyres traction was so bad that it was gliding on interstate. Got swapped into an AWD at ABQ airport and it was much better after that.