There's not a lot of electrified track in the US. The distances are just too great and our railroads are freight-first, passengers second (the opposite of Europe).
Even so, the passenger trains don't make abrupt starts/stops like the freight trains do, because people would complain. :)
Actually there used to be a lot more electrified track in the US but the freight railroads tore it out to reduce capital ratios and allow tall-stacking containers.
It's the difference between "should be" and "reality". (I blame precision scheduled railroading for creating freight trains so long that they can't use sidings)
Even so, the passenger trains don't make abrupt starts/stops like the freight trains do, because people would complain. :)