Americans don't generally have a negative thing to say about public transportation. Americans, however, prefer to drive their own vehicle for many reasons. For one, being independent, not relying on a schedule. Not worrying about missing their transportation and catching a later one, then being late to the arrival of their destination.
I don't know where you live, but in the big cities of the U.S., public transportation... isn't exactly hygienic. You will smell urine. You will encounter chitty people. You will be spending time reading all the random chit people write/scratch onto the walls and glass. You will sit on uncomfortable chairs, might even touch someone's chewed up gum by accident.
I've seen some chit both in city busses and trains but this was in Chicago and some parts of NY. Never would I ever want to live that life. Ever.