Right - public transit needs to be usable in the place you’re traveling to if you’re going to take a train. This is why a lot of people would rather drive from, say San Francisco to Los Angeles. Suppose you were to take a train instead. Then… great?! what would you do next? You wouldn’t have anywhere to go, so you’ll need a car anyway. You’d either have to rent one or just skip the train and do the drive instead.

Probably a lot easier and feasible in my opinion to build the local public transit first, and then focus on the regional/national transit system.