I travel for work -- use I-90 to I-15 at Butte, Mt. Head South and the highest pass is Monida at the Mont/Id state line.
Two large truck stops at Rocker (Butte, Mt.). Heading South, there is a rest area just north of the state line big enough for any rv just past the truck scales. Blackfoot, Id has a Wal-Mart just off the freeway, and there are a couple large rest stops too.
Salt Lake is pretty high and can get lake effect snow, but for the most part, it will be pretty smooth sailing. Oh, there is a Cabelas South of SLC but I can't recall the town---it has rv parking and a dump too.
The book "NEXT EXIT" is a good source of info. You won't have any problems, the U S has wimpy weather compared to Canada.
