@ColeSloth "So you’re saying you have like 30 with populations at or over 100k? Ok. Wow. The US has over 330 like that."
So you should have many more pairs of cities that should support rail.
And once you have a pair of cities that support rail, you can have stations in each of the towns between them.
Even if they're only a couple of hundred people.
"A rail system doesn’t sustain when people are trying to get from one place to so many different destinations and you can’t claim it can, when it’s literally never been created on a scale of anything similar to the US."
That's all the places where it's viable for a commercial operator to have railways based on freight.
So a decent starting point would be just to run passenger services along those existing freight corridors, as Brightline did in Florida.
And frankly, if the US had spent a fraction as much on rail as it has on propping up the auto and oil sectors, it'd be viable.
(By the way, before the World Wars, the US had even more railways with a smaller population. Many US towns are where they are because of the railways.)
"For everyone to get to their destinations..."
You have a hub where many lines converge, or lines that cross one another.
If trains are timetabled to arrive and leave at the same time, or arrive frequently, you transfer.
So think of multiple lines between pairs of big cities, serving many smaller towns in between.
Even if you're the only person travelling between one tiny town on one line to another tiny town on another line. And you're the only person making that particular journey in a given month.
If there's a station or hub you can transfer at, you can make that journey by rail.
"...without it taking many extra hours of travel time..."
Trains are significantly faster than cars, and don't get stuck in traffic.
"...and tons of them would be going places where they may only have a handful of passengers on board..."
If it's on a line between two larger cities, even small towns are viable for rail. If it isn't, you run a frequent feeder bus service to the nearest town with a train station.
"a train running with just a dozen passengers is a hell of a lot worse for the environment than a dozen cars. A lot worse."
You do realise electric-powered trains exist, right? And electricity can come from renewables? And renewable energy can be stored?
"That can’t happen in the US unless travel destinations limit themselves way down, which cuts a lot of people off from using them."
The problem is that the US has government-owned roads and not rail.
The problem is the US spent $597 bn (adjusted for inflation) building the interstate highway system, instead of investing in rail.
Half a trillion subsidy for the interstates alone.
The problem is that the US government mandated planning codes that make it illegal to build the types of developments that support rail.