UA doesn't sell one way tickets from LAX to LAX via JFK, so if your LAX-JFK flight happens to misconnect to JFK-LAX, the only reasonable accommodation to expect from UA is to rebooked on the next available flight. There is no way you are entitled to hotel accommodations at JFK due to late arrival, regardless of whose fault the delay is, because JFK is a destination point not a connection point.

That said, I think most of the p.s. arrivals through the late afternoon make a same day return to the west coast, so as long as you are scheduled to arrive JFK in the afternoon you should be fairly safe because your inbound plane will be used for a return trip to the west coast.