Because we have people spread out all across a massive landscape in the USA, it’s not ever likely to be feasible to build public transport to reach everyone. No, we don’t all live in the big cities and we never will.
Personal transportation will always be a necessity for Americans, except for those who choose to live inside large cities that do have public transport. EVs with Sodium ion batteries would vastly improve our emissions and eliminate the problem with sourcing Lithium batteries’ minerals.