100km return, or 30 miles each way, that's not far at all. I used to drive 50 miles/80km each way into London 4 days a week when I worked in an office. My wife still does a 100km return trip to work. I have colleagues that commute 7 days in 14 on a 250km round trip into West London.
Your 127km one way train is about the same as the new Reading-Shenfield Cross London service which runs 6 times an hour 18 hours a day (well will do from next year), and less than the 160km Bedford-Brighton Thameslink service. It's pretty much the "Greater London Area", although that term is of course steeped in politics. The Paris RER D line is 190km and runs 466 trains a day, and is a "greater Paris area" train system
The Greater Toronto Area has broadly the same population as the Frankfurt Rhine-Main area, but is only half the area.
The "Slovenia is only 75km wide" claim is meaningless. Greenwich, CT to Oakland NJ is 75km and crosses the entire state of New York, a state with 10 times the population of Slovenia.
Indeed talking about New Jersey and Slovenia, they're a similar size, but NJ has about 5 times the population of Slovenia.
If something works for Slovenia, why doesn't it work for New Jersey?
So why is Toronto so small compared with Europe?
It's not a Geography problem, the challenges of serving the tiny number of people that like in rural North Dakota are a cruch to hide America's other infrastructure failings.