Fun fact: 8M Swiss do 1.8x the passenger kilometers of all of the US combined [1]. I'm pretty sure you have enough densely populated areas in the US that are larger than Switzerland, especially in the East coast.
There is a bit of mentality too - for Swiss, railroads are part of culture, train stations are always at the heart of a city, and even small places are connected. Train infrastructure is dense.
but it is bloody expensive, plain ticket for 20 km ride costs as much as 5 hour ride on fast train back home. everybody here buys early "ticket" that halves the prices of all tickets for 180 usd
[1] https://en.wikipedia.org/wiki/Rail_usage_statistics_by_count...