I did this over two weeks and it wasn't bad. I only needed two rideshare trips: one for a wedding in OKC, and the other was to get to and from the National Museum of Transportation in STL. Everything else was public transport or on my own two feet. If I were to do that again I'd skip OKC if I didn't have a reason to go there, and perhaps take the California Zephyr instead of the Southwest Chief and then head down the California Coast by way of the Starlight.
I've also been on the train from San Diego to Vancouver, BC over three weeks by train. The only car ride was a generous friend who drove me to Emeryville instead of having to take BART and walk a bit. Stops were Santa Barbara, Oakland/Emeryville/San Francisco, Portland, Seattle, and Vancover.
Some major cities have much better public transportation than others. In my experience: the Northeast Corridor, San Francisco, Chicago, Seattle, and Portland (Oregon) are all really good by US standards. Denver, Los Angeles, and San Diego are in the next tier down but you may have to be more deliberate in planning if you're going outside of the main transit areas. St. Louis, Orange County (California), and any major city in Texas have pretty bad transit, though you can probably scrape by depending on what you want to see and how you feel about rideshare. Sacramento doesn't have great transit, but I don't think you really need it. OKC and a lot of cities in the Midwest I haven't mentioned here have non-existent transit. Google Maps covers transit in the US pretty well, so you can run a few checks before booking a stop in a city.
Since the OP asked: the next big Amtrak trip for me is likely from Boston to Sacramento over two-ish weeks via Acela, the Cardinal, and the Zephyr. That would cover pretty much every line on Amtrak that is on my bucket list. Philadelphia, southwest Illinois (for the Quad Cities), and Omaha would be my top three stops on that trip outside of Boston.
I've also been on the train from San Diego to Vancouver, BC over three weeks by train. The only car ride was a generous friend who drove me to Emeryville instead of having to take BART and walk a bit. Stops were Santa Barbara, Oakland/Emeryville/San Francisco, Portland, Seattle, and Vancover.
Some major cities have much better public transportation than others. In my experience: the Northeast Corridor, San Francisco, Chicago, Seattle, and Portland (Oregon) are all really good by US standards. Denver, Los Angeles, and San Diego are in the next tier down but you may have to be more deliberate in planning if you're going outside of the main transit areas. St. Louis, Orange County (California), and any major city in Texas have pretty bad transit, though you can probably scrape by depending on what you want to see and how you feel about rideshare. Sacramento doesn't have great transit, but I don't think you really need it. OKC and a lot of cities in the Midwest I haven't mentioned here have non-existent transit. Google Maps covers transit in the US pretty well, so you can run a few checks before booking a stop in a city.
Since the OP asked: the next big Amtrak trip for me is likely from Boston to Sacramento over two-ish weeks via Acela, the Cardinal, and the Zephyr. That would cover pretty much every line on Amtrak that is on my bucket list. Philadelphia, southwest Illinois (for the Quad Cities), and Omaha would be my top three stops on that trip outside of Boston.
