Two cities can only be linked effectively by rail when there aren't stops between them. That's impossible in America, where suburban areas are the political battlegrounds while cities are single-party fiefdoms.
What happened is that, historically, Baltimore-Washington was mainly served by the B&O, whose Baltimore station would have been right next to Inner Harbor (Camden Yards is essentially built on old railroad property). When passenger service was consolidated into Amtrak, the Northeast Corridor instead chose to use Pennsylvania Railroad trackage instead of B&O from DC to NYC, and the freight trackage in the corridor consolidated onto the B&O tracks instead. The resulting residual commuter rail line has the standard commuter rail/freight rail politics going on that limits the number of trains that can transit the route.
That's really not a lot, especially between major cities.
Comparing trains from London is not really fair because virtually every train in the south ends up in London eventually. Somewhat tragically, I once tried to take a train from Watford to visit Hatfield House, some 14 miles away. I think it took me 3 hours getting in and out of London :-)
OTOH between Macon (pop 34000) and Lyon (pop 500000) there is up to 4 trains / hour at commute times (1 an hour otherwise), over a slightly longer distance.
You really have to look at the metro population.
This is depressingly familiar situation in the UK too (not sure about the rest of Europe). Usually, it's not politics that prevent more useful connections being made, but a lack of investment to do the necessary small bits of engineering.
As a consequence trains from Baltimore run a bit more often then once an hour - though I don't take Camden Line (It's for losers) so I don't know what the overlap is exactly.
Why is this? Full of tourists?
[0] https://www.google.com/maps/place/University+of+Baltimore+-+...
[1] https://www.google.com/maps/place/Penn+Station/@39.3071436,-...
99% of all the light rail "lines" ride the same track. The Penn-Camden "line" veers off the main tracks right at that Mt Royal stop (MICA/UB), and only goes to Penn, then back to the main line at Mt Royal, then headed to Camden Yards. It's probably the least common "line" to see.
Culture is not something which happens automatically - sometimes its driven by corporates, and the stronger the incentives for the corporates, the harder to resist, until the only one capable of doing so is the government.
https://en.wikipedia.org/wiki/General_Motors_streetcar_consp...
In this case culture (the shifting demographics that led to the initial growth of the suburb and the self-perpetuating cultural enshrinement of same) is what led and government/corporations followed.
What the ground truth was then isn't recorded in history. There are post-facto interpretations. I would argue if the incentives were laid correctly, there was no reason for suburbanism to necessarily lead to growth in automobile consumption.
The US motor companies had a massive clout. Given a choice back then (and the big roads due to the post-war expansion) it possibly made it easy to convince people that a car was a superior and more personal form of travel (think pre-ubiquitous air-conditioning). That's when you need government to think ahead, especially at the local level.
1. A lot of existing big cities post-WWII did, in fact, grow commuter rail out to the expanding suburbs. If you live in the suburbs (say Westchester County in NY) and work at a bank in Manhattan, there is pretty good rail service.
2. But, a lot of the suburban expansion also included companies locating out in the suburbs. For a variety of reasons (including "white flight") a lot of cities became unpopular places for professionals to live so it made sense to locate companies where the people were. NYC almost went bankrupt. Boston was losing population into the 90s. So, for a significant period of time, you had a lot of people dispersed around suburbs (and still do) and that's hard to accommodate with transit.
In Boston, for example, there was not a single major tech employer in the city by the mid 90s or so--when Teradyne moved out--all the "Route 128" companies and others were in the suburbs/exurbs. (I would bet that, at least leaving out biotech/pharma, most tech employment in the Boston area is still in the suburbs--as indeed it is in the Bay Area.)
A really weird experience I had while visiting CA (SSF specifically) was seeing a fast food place - I think it was Wendy's? - that wasn't reachable by foot in any clear way. Similarly there wasn't any obvious sidewalks or bike lanes on the highway between Brisbane and SSF, and while that _is_ as 2km walk, I'd still expect it to be _possible_.
I mean, I've been there for a week, and I'm sure it's possible to work things like that out if you live there longer. Maybe there's an entrance to the county park I didn't notice, or I don't know, a tunnel. But where I live, walking is far more intuitive than that. A tram might help, but it won't solve it.
Most cities in the US are simply not equipped to deal with any sort of large population growth due to the incredibly bad infrastructure we have in place and zero motivation to improve it.
I then moved to the Bay Area, and now I'm driving everywhere.
Even to towns that I could actually reach with BART (which are not many), I would then face the problem, as you laid out yourself, to actually get around there.
One begs to ask the question, Why do Americans need to live so sprawled out? I think the difference is not just one of geography, it’s cultural. It makes sense for Japanese to live in close quarters and there are benefits and negatives for doing so.
Look at France, Germany, Belgium, UK Etc they’re allrelatively population dense countrirs with far more hopeless train networks.
Also, rail roads are not walkable, so they cannot be shared with pedestrians, so this limitation forces create two separate roads: one for pedestrians, bicycles, cars, etc., and second one for rail transport. Trams can be mixed with regular road traffic, but trams cannot use regular rail roads because of different construction of rail road.
Also, rail roads are prone to Single Point of Failure problems. To prevent SPF, multiple redundant routes must be built, with lot of expensive junctions between them.
Also, you must schedule your travel.
So, we need something which 1) can be shared with regular road traffic like trams, 2) can deliver loads of cargo efficiently like rail or metro, 3) can be connected to every house like regular road, 4) can be navigated by any car at any time of day or night, 5) be cheaper than regular road for road, cart, maintenance, recycling, 6) can provide power to carts, 7) can provide navigation and scheduling service to carts, 8) be with low delay (fast).
Regular road is 1,3,4,±8. Uber is 1,3,4,5,7,8. Aero-taxi is 1,3,4,±5,7,8. Trams is 1,2,6,7. Metro is 2,6,7. Rail is 2,5,6,7.
Edit: Tram-train is 1,2,5,6,7.
Actually, they can. https://en.wikipedia.org/wiki/Tram-train
So no state in continental Europe wanted to be on the losing side of a railway gap.