I agree, drive through the mountains. Half of the train trip across the Rockies is at night. Many nice places to stop on the way through.
I crossed the Prairies once on the way east- not so bad. The blue of flax, the yellow of Canola and mustard, and the green of the rest make the fields interesting.
I took the Canadian route through eastern Manitoba and above the lakes- land of one hell of a lot of lakes, and treed country- interesting to see once but not twice. This was the slowest-seeming part of the trip.
I don't know your destination, but if it is the whole way east, I enjoyed two trips along the St. Lawrence and into New Brunswick, and on to the Gaspe. I could spend many weeks in this region.