You are greatly minimizing the problems that most Americans face. Most American cities are not dense enough to require good public transportation options (the exception being NYC); without enough density (and lack of public funding), public transportation is short on cash and often very inconvenient. If you miss your bus, you have to wait an absurd amount of time for the next available one. Also good luck with hauling in all the groceries and stuff you need into your suburban home using only buses.... simply not possible.

So there are multiple factors at play. Short of a massive change in the way American cities are designed or some innovation that greatly reduces the cost of building public transportation, cars will continue to be something Americans absolutely need for surviving.