Toyota's problem was the boxed frame that made the truck so strong wasn't made with any drain holes. That wasn't a brine problem, it was an engineering problem.
Well if it's not a brine problem... why are there 30 year old Toyota frames that are still solid in southern and western states... and five year old frames needing to be replaced in the rust belt? Boxed frame or not... there's a difference in how long they hold up in states that use brine and those that don't.
I suspect in more frozen north states things are a bit different. Because we get heavy wet snows and big temperature swings which seem to require more than sand.
We have mountains and ski resorts that make eastern climates look temperate. High deserts with drifts and cutting winds. The Dakotas, Montana, Idaho are all comparable to Michigan and further east in snow totals and temps.
Also, reading the trucking trade publications they often talk about the different chemicals they use. *** chloride this and such, and how significant the corrosion is because of some of the particular chloride solutions being used in particular areas.
And I suspect there is more rust in the Dakotas/Montana/Idaho than in Arizona, but the rates of rust failures is still nowhere near what it is in the rust belt.