> people chronically underestimate the cost of driving (and many of them are fixed costs)
Once someone has paid the fixed cost of owning a car, that cost is sunk and shouldn't be factored into calculations for individual trips. The only thing that matters at that point is marginal cost.
For public transportation to be competitive, the overall public transportation system has to provide a level of service that makes it feasible for many people to not own a car at all. For example, having great inter-city train service doesn't help if I need a car to get to the train station. If I have to own the car anyway, and the marginal cost of driving is lower than the marginal cost of taking the train, I'm going to drive.
In most European countries, the overall public transportation system does provide this level of service. In most places in the US, it doesn't. A significant part of the reason for that is simply that people in Europe and people in the US have a different mix of preferences. Many more people in the US do not want to live in population dense areas that can support a public transportation system that makes it feasible to not own a car. (I'm one of them: I have lived in population dense areas and I know from experience that I prefer not to.)
Once someone has paid the fixed cost of owning a car, that cost is sunk and shouldn't be factored into calculations for individual trips. The only thing that matters at that point is marginal cost.
For public transportation to be competitive, the overall public transportation system has to provide a level of service that makes it feasible for many people to not own a car at all. For example, having great inter-city train service doesn't help if I need a car to get to the train station. If I have to own the car anyway, and the marginal cost of driving is lower than the marginal cost of taking the train, I'm going to drive.
In most European countries, the overall public transportation system does provide this level of service. In most places in the US, it doesn't. A significant part of the reason for that is simply that people in Europe and people in the US have a different mix of preferences. Many more people in the US do not want to live in population dense areas that can support a public transportation system that makes it feasible to not own a car. (I'm one of them: I have lived in population dense areas and I know from experience that I prefer not to.)