[dagw]

It's not the size of the city per se. that's the problem in the US, but that very few people live and work actually in the centers of those cities. They're all dispersed out in the suburbs. Take an avg 50-80k population city in the US and draw a circle, centered in the middle of town, that encompasses say 60% of the cities population, now do the same with a European city of the same size. The circle for the European city will almost always be much smaller, meaning it's much easier to cover a significant proportion of the population with a reasonable public transportation network.