An experiment.
USA Greyhound.
Boise > Chicago.
39 hours.
Driving ... according to Google Maps.
Boise > Chicago.
25 hours.
So you could spend 39 hours on a bus.
Or you and a friend could tag team for 25 hours, stopping where you want to stop to eat or rest etc. You could even stop for 13.5 hours at a hotel, mid-drive and get a decent night's sleep, and still arrive before the bus!!