Most people don’t do it in one go. Building in stops, Chicago, the Rockies, a national park, a city or two, turns the crossing into a one- to two-week trip where the train is the thread between places rather than a marathon.
Straight through vs stops
The California Zephyr from the Bay Area to Chicago alone is about 51 hours over two nights; add the Chicago–New York leg for the full width. Splitting it across several stays is far more comfortable.