You said the USA was big. Now you're saying population is the important thing. Combined that's population density, so does Maryland have this? Connecticut? etc.
On the density front, NYC is famously high density, and yet so far as I can tell a monthly pass for just there is double the raised price this ticket will be next year: https://new.mta.info/document/118601
On the density front, NYC is famously high density, and yet so far as I can tell a monthly pass for just there is double the raised price this ticket will be next year: https://new.mta.info/document/118601