I was with you until the last sentence. Your train trip that crosses two continental divides is still going to take you more than a day. Even a "spare no expense" rail project isn't going to make that cross-country trip palatable for most travelers.
WTC/Penn/14th street are centrally connected stations that should have a direct connection to JFK.
Run an express A-C-E train from central-park, 34th, 14th, WTC, Atlantic, Jamaica, JFK. It should not be that hard. While we are at it, run an express downtown manhattan to Newark train/BRT too. LaGuardia is....hopeless.
But oh so close!
https://news.ycombinator.com/item?id=26589001
;)
If the claim was to build a sub-8-hour LA to NYC train that’s obviously not going to work because of physics. If the claim was we need rail to LAX and JFK that’s silly because both are already served by rail.