Hi, and Welcome to the Great American Road Trip Forum.
We really do not do 'must sees' on RTA. A road trip is unique for each and every traveller. One person's must see, is another's must pass by. Starting and ending in Calgary, one omission I see is Alaska. It would be well worth tying that into your plan. You might like to look at my six month trip in 2012.
With some 15 months yet to go, the very best thing you can do right now is to get yourself a good wall map of North America. I like the National Geographic's map which is available from Map World in your capital city. I have the laminated version.
Use post-it notes to mark the places which are your must sees, and see if that starts to lay out a route. Members here will help you refine it and give further suggestions. However the start will need to come from you with some specifics.
From where I sit, I would say you can't be more wrong. The middle States are spectacular. Alberta, BC and the Yukon are very different from Wyoming or Colorado. Having driven several times through the Rockies in both Canada and the US., They are hugely different. Maybe MT and ID are a bit like the land north of the border.I imagine the middle states Idaho/Wyoming and Montana are similar landscapes to Alberta (mountains, lakes etc)
I should also mention that it will pay you to bring your local automobile club membership (RACV, NRMA, etc.) with you - unless of course you are a current member of a Canadian automobile club. All of them will give you access to free maps and tourism information from the AAA and CAA.
Detailed maps or a Road Atlas could also be very useful in the planning stages. If you have family in North America who are members of their local club, they may be able to send these to you. I like having detailed maps of all the States in which I travel. A Rand McNally road atlas can be ordered from the Shop on the green bar above. You'll have it in two or three weeks.
Lifey