Make sure you check with Amtrak that the stations for starting and stopping your trip still offer baggage service. Amtrak has made many service reductions that include making many stations unmanned. This means the station no longer offers baggage service. This means you can't buy a bike box or even put the bike in the baggage car without a box. Some trains may still have a separate car with bike racks but I am not sure which train have that car. I had to cancel my trip because they changed the service in major cities. I wasn't notified of the change even though my fare included the bike fee. You have to call Amtrak. The website doesn't include the changes they recently made. If you just go by the website it may say the station offers baggage service but when you get to the station they will tell you no baggage service is available.
Damn, it's really terrible that you had to cancel the trip! So frustrating! Thanks for the heads up.
In case this is useful information for anyone else: I dropped by the Emeryville, CA station yesterday (July 27, 2020) and asked the agent for details about bringing a bike. It's operational there. He also asked where I'm getting off (Grand Junction, CO) and he said that would work.