I recommend driving from New York to San Francisco as a research project. It will take you through Omaha, across Nebraska on the Overland Route (or Lincoln Highway or I80 or the Oregon Trail -- fortunately your sister is unlikely to die of dysentery these days) and along the Platte into the Wyoming Basin, then down into Ogden, across Nevada, over Donner Pass, and down into Sacramento before finally reaching the Bay Area.
The most direct route hasn't changed because the geography hasn't changed. You'll spend a thousand miles going up and down mountains and valleys. Most of it will be sparse desert and bitterly cold in the winters and broiling hot in the summer. Sparsely populated -- even Reno is only 1/2 a million people and everyone Casper, Wyoming will fit in a Division I AA football stadium because it's all a long way from anywhere of much importance except to the people who live there.
Though I said I recommended it as a research project, I really recommend it because driving it will probably change your life. It's beautiful and remote and awe-inspiring in a way that the average place that people live isn't and doesn't convey over a few hours in the air 8km up.
There are only four practical rail routes across the US. One further north through Montana and down to Portland used by the Great Northern. One south of the Oregon Trail that follows I40 over the Colorado Plateau south of the Grand Canyon. And finally, the only all-weather line across the width of Texas through El-Paso and southern New Mexico and Arizona. It's the reason for the Gadsden Purchase.
The highway system is what public transit looks like in the US because the US is what it is. Increasingly vast, rugged and remote once you cross the Mississippi. Vast, rugged and remote in a way the tends to make it map poorly between the way we tend to think about political geography relating to physical geography.
The reason there isn't high speed rail across the US isn't in the details. It isn't because of some great conspiracy. It's in the course grain of physical geography. It's not a lack of imagination. It's an abundance of rail expertise applied over the better part of two hundred years.