I live in the United States and never heard of a rust proofing option either, and I live in the wet PNW. It’s a big republic separated into 50 individual states. There’s a lot of variance; some places have hustle but most don’t.
Rustproofing is less necessary on modern cars than it used to be, and dealer rustproofing is pretty much universally worse than third-party (RustCheck, Krown, Corrosion-Free, etc.) but if you drive on salty winter roads for 1/3 of the year it definitely helps things not rust out on you as soon as they would otherwise.
Furthermore, ice alone is basically inert at the timescales that we experience. It would take eons for pure ice to react enough for visible rust to form. Even if it was cold enough for salt water to freeze, the difference would be negligible because salt and water separate from each other as the water crystallizes into ice.
Also, we salt the roads here. Our freeze/thaw cycle is more frequent allowing for rust reactions to occur throughout the season, whereas a colder climate will only see reactions in the spring. There is no shortage of rust here.
My wife said that when she moved from upstate New York to San Francisco, the first mechanic she took her car to asked whether she drove it to the beach a lot. He was not used to seeing the effects of road salt.