In many of those cities, the older, walkable neighborhoods have been left to decay, with gutted transit service, failing schools, and many fine old structures demolished to build parking lots or simply let to collapse., while many residents and jobs have decamped to auto-oriented exurban areas. But that is to a large degree a policy choice designed to maintain residential segregation, and something which can and must be reversed by different policy choices.

It is more the Sunbelt than the Midwest where a vast majority of the infrastructure was built in the postwar automobile era, and most neigborhoods (if you can even call them that) are nearly inaccessible to the pedestrian, cyclist, and mass transit user.

Now, we have a hundred years of data and experience with the automobile, and it's become obvious that the fossil fuel powered car isn't a good long-term solution to the urban and suburban transportation problem. Literally everything about them is bad for the world, gathering and burning the fuel, the destruction required for their roads, the massive amount of space needed to store them, and the death and destruction they cause daily. Electric (and other alternative fuel) cars are less bad, but only in one small way, they address a single issue in an inherently flawed model.

You say that Europe has an advantage because it's cities are much older, but it's important to understand that the Netherlands and Denmark were both on the same auto-centric trajectory that the US was on coming out of the World Wars and industrialization. Denmark only started rebuilding their cycling infrastructure after decades of disuse when the energy crisis in the 70s made using a car extremely expensive. In both countries, people realized just how bad cars were. The deaths of cyclists (especially children) sparked mass protests where people demanded cycling infrastructure, and they got it. They were able to convert a car-focused city (perhaps less so than Los Angeles or New York, but still) into a bike focused city. They were able to do it, why can't we?

Modern Rotterdam was built almost entirely after World War II, the same era that many American Sunbelt cities were built to their current size. In Rotterdam, the mode share is: 5% pedestrian, 14% cycling, 25% transit, 56% automobile. This is very auto-oriented for the Netherlands, but still more than twice the 6% bike mode share of Portland, Oregon, a mid-sized American city famous here for loving bikes.

That illustrates quite well that America's near-exclusive automobile use in many cities is a matter of city planning and development policies in this country (wide, high-speed roads optimized for moving the maximum number of cars, minimum parking requirements, minimum lot size requirements and setbacks, strict zoning laws separating residential from commercial uses and single-family homes from apartments) mandating a suburban form that makes non-automobile transportation difficult or impossible. It's not simply a question of the age of a city.