It’s not viable. The United States is too wealthy for passengers to waste days on a train. They’ll simply fly in 4 hours. Furthermore, that Chicago to Los Angeles train already exists and runs daily.
To travel from NYC to Chicago on Aug. 21st:
Flight: $124 nonstop (2hr 40 min) or $85 with layover (7 hours)
Greyhound (bus): $170 (23.5 hours)
Amtrak: $144 (19.5 hours)
If you value your time and/or your money the flights usually win