Exactly. HSR was a great idea for the second half of the 20th century in relatively dense countries like Japan, France, and Germany that already had good local rail infrastructure. It fills a gap for travel between dense population areas 100-500km(?) away, where road travel is too slow and air has too much overhead with last mile. The benefit was that train stations could be built directly in population centers and connected to local rail, cutting down on last mile travel times of air.
The US is more spread out, tilting in favor of air, and local rail is less abundant + our interstate highway system is more mature + gas is much cheaper, tilting in favor of cars. The value of rail is squeezed from both sides.
Now comes along a great technology that can bootstrap off existing infrastructure (road), offers the same benefit of time not wasted focusing on the road, whose cost burden is shouldered by those that use it (purchasing cars), and can incrementally be improved over time (higher speeds, drafting, separate lanes, etc). That further puts the squeeze on travel between shorter distances, which can make the promised SF-LA trip in <6 hours (instead of 4* via air) that can be reduced to 4 over time with faster speeds.
Driverless tech doesn't even need to work in places outside the controlled environment of a highway for these benefits to appear. Politicians could make it happen a few years sooner by making it more appealing (much as they did with hybrid carpool stickers) by creating a special driverless car lane on highways, separated by cement barriers. Although I think that's not as elegant as just bootstrapping on carpool lanes, it is possible now and would definitely spur car companies to upgrade their driverless systems to whatever requirements would be needed for that environment.
Certain parts of the US (east coast corridor) seem to me to be the only places in the US that could actually benefit from the HSR equation, but they have big right-of-way issues and there's a lot of political coordination that needs to happen. Amtrak's been trying for decades.
* Air calculation: 1.5h pre-flight, 1.5h flight, 1h post-flight