> The point of cross continent rail travel is not being cheaper than air at all, it is about seeing and enjoying the country and the route, there is no easier or cheaper way to do that.
Amtrak isn't useful for that. For see the continent you need to get off the train for a few hours here and there to see something. That means flexible tickets; more trains so you don't have to spend a day in a small town with 3 hours entertainment, and enough space that you can make a last minute decision to see some little tourist trap for the fun of it knowing you can get the next train.
> A road trip would be both more expensive (fuel, hotels and maintenance/rental),
Very much it depends. If you are single Amtrak is cheaper (coach seats). a family is a lot cheaper to drive, since most of the costs are fixed for everyone. You likely own the car and so are making payments anyway. Gas is the same for 1 person or a full car. Hotels are rented per room. My last trip I needed a rental car to get to the family reunion 1 hour from the station, just the cost of a rental car would have paid for gas and hotel to drive my own car (the strenuous miles is why we took the train anyway, but it was more expensive than driving)
> There is quite little to see in a cruise if not near a shore
I've never been on that type of cruise (they exist, just not what I've been on). What I've been on the sea days were near shore taking in the beautiful scenery (you don't take an Alaska cruise for the ports, you take the cruise to watch the shore on sea days), or the ship hopes between islands at night and so you are at a port all day (though next time I think I'd get a resort and stay on one island). Beware.
Amtrak is often a great choice to get around. However there are problems and they are not to be overlooked.
It is a 12 day one way trip that includes plenty of overnight non train stays(i.e. hotels), full day sight seeing stops etc .
You can mix local car rentals to take extended side trips add much longer breaks with hop-on/hop off if you plan to do so.
There are national park themed trips specifically, or number of great regional options or other cross country journeys like LA to NOLA etc.
It will be never be perfect exact fit to your specific tastes and needs, no public transit can ever be,. However that doesn't mean it is not a great option for a traveling family vacation with sight seeing and breaks, where you can actually spend quality time with the family rather than just looking straight at the road all day, while everyone else is on the phone.
Amtrak isn't useful for that. For see the continent you need to get off the train for a few hours here and there to see something. That means flexible tickets; more trains so you don't have to spend a day in a small town with 3 hours entertainment, and enough space that you can make a last minute decision to see some little tourist trap for the fun of it knowing you can get the next train.
> A road trip would be both more expensive (fuel, hotels and maintenance/rental),
Very much it depends. If you are single Amtrak is cheaper (coach seats). a family is a lot cheaper to drive, since most of the costs are fixed for everyone. You likely own the car and so are making payments anyway. Gas is the same for 1 person or a full car. Hotels are rented per room. My last trip I needed a rental car to get to the family reunion 1 hour from the station, just the cost of a rental car would have paid for gas and hotel to drive my own car (the strenuous miles is why we took the train anyway, but it was more expensive than driving)
> There is quite little to see in a cruise if not near a shore
I've never been on that type of cruise (they exist, just not what I've been on). What I've been on the sea days were near shore taking in the beautiful scenery (you don't take an Alaska cruise for the ports, you take the cruise to watch the shore on sea days), or the ship hopes between islands at night and so you are at a port all day (though next time I think I'd get a resort and stay on one island). Beware.
Amtrak is often a great choice to get around. However there are problems and they are not to be overlooked.