The question is flawed. The fact is that most US public transportation is awful. This is quite literally by design. In the 1950's, a conscious decision was made by policy makers to begin neglecting public transportation and to start investing public money in road systems in a big way. This is what built the interstate system, for example. A few places, Portland Oregon, for example, took some of that interstate money and invested in public transportation. Portland's system is actually quite good, now, and if you lived there, you would probably use it quite a bit.
But if you live in one of the countless suburban freeway islands, using public transportation is absurd. The way the roads and infrastructure are laid out make it almost impossible to install an efficient public transportation system. In many suburban areas, the mere act of walking somewhere is almost impossible or illegal.
There is a truism in transportation design: the freeways make the sprawl. And the converse is also true: passenger rail transportation increase creates clusters of density. Evidence of this can be seen in the observation that since the massive reduction of passenger rail transportation in the US, there have been almost no new dense walkable diverse large scale downtown core cities established. The big ones, New York, Chicago, etc. were established during the age of passenger rail. Most new cities are freeway places, and usually don't achieve the density of the older cities. By choosing to build freeways, we chose to create suburban sprawl. The only way to get out of this trap is to slow the building of freeways, and to increase investment in passenger rail.