If this is the only camera you are taking I would forget angle and think about distance, any lens can focus at infinity, but if you are doing a one camera one lens trip you want something that can focus across a table, and maybe inside a car. Yes the American West is grand and beautiful, but so are the people you will be traveling with.
I travel with a pocket Brownie for Medium format, and a Nikon 35mm with a Tamron 28-200 attached, I have a Nikon 28-200 that is 1/5 of a stop faster, but the Tamron focuses down to about .3 Meters and the Nikon only works at a little over a Meter. I learned that the Tamron lens is not quite as good as the Nikon when it comes to sharpness, but for taking photos of family, signs, details, plants, and anything that I can't photograph at over 1 Meter the Tamron is the way to go.
Lets just say a family vacation with lots of great photos of the sights is less fun than a family vacation with photos of the family being silly and doing family type things.
Learn from my mistake and bring the lens that will work close as well as far.
If you are bringing a snapshot camera for photos of the family then take the 55 for your scenic work.