Starting in the 1940s, the USA stopped using passenger transport on trains in favor of automobiles. In the 1950s, a huge highway system was constructed/upgraded in order to make military mobilization effective. No similar program was ever executed for rail systems.

Today, all long-route passenger service is handled by Amtrak, a for-profit corporation which is both a monopoly and subsidized by the Federal government. The only electrified Amtrak rails are in the northeast, running from Washington DC past NYC to New Haven, Connecticut, and then a different electrification scheme from New Haven to Boston, plus a route across half of Pennsylvania. Everywhere else across the country, long-haul rail is strictly diesel.

The person you quoted is talking about the portion of the NYC - Boston route just north of NYC, going through a fairly expensive area called Westchester. It is noted for high incomes and high property taxes. The train tracks are not in good repair and there are too many at-grade road crossings. The result is that Amtrak is chronically late.