I think you fail to grasp just how big the US is. Driving from Chicago to Minneapolis is ~430 miles/ 6.5 hours depending on weather and traffic. Every 10 miles or so there is an exit and usually some small town. Every 50 to 100 miles a bigger town.Why do people trot this out every time? Driving or traveling across the US isn't particularly relevant to most people's life experience. Ok, I'll bite.
Yes, the United States is big, but some areas are more dense than other and would need good heavy investment in public transit infrastructure. For example, the north eastern corridor would in particular benefit from investment in true high speed rail.
There's also the need for investment in freight infrastructure, especially if we want to take off more trucks off the road. This is a safety benefit too. Less vehicles on the roads just mean less people risking their neck.
Now let's talk more local public transit.
Atlanta for example, really need to expand heavy rail. Traffic there is one of the worst in the country. MARTA at time outpaces cars, even with all the stops they have to make. Rather, a lot of time is eaten up just waiting for the train. A more frequent schedule would help here, but Georgia would need to actually contribute funding to make this possible. If they extend it more into the surburb, I would have less of an incentive to move. As now, I am considering moving because of how frequent I commute into Atlanta.