Another reason to ride a folding bike! Here's what Amtrak has to say about folders:
Folding bicycles under the dimensions of 34" x 15" x 48" (860 x 380 x 1120 mm) will be allowed onboard all trains in lieu of a piece of baggage.
Only certain passenger cars can accommodate folding bicycles as carry-on baggage, otherwise they must be checked.
Only true folding bicycles (bicycles specifically designed to fold up into a compact assembly) are acceptable. Generally, these bikes have frame latches allowing the frame to be collapsed, and small wheels. Regular bikes of any size, with or without wheels, are not considered folding bikes, and may not be stored as folding bikes aboard trains.
You must fold up your folding bicycle before boarding the train. You may store the bike only in luggage storage areas at the end of the car (or, in Superliners, on the lower level). You may not store bikes in overhead racks.
I would suggest that you watch your bike at stops so that someone doesn't grab it when exiting the train (when I rode the SW Chief from ABQ to L.A. almost anyone could have grabbed someone's luggage, it appeared to me.) Put it in a bag so that it doesn't look so much like a bike, especially an e-bike.