NC Flyer

Your flight was into London and even though not on a European carrier you will be covered by EU regulation 261/2004. The compensation from that would more than cover the loss of your hotel room. However, the chances of success are small given that the cancellation was due to a maintenance problem and they will claim safety. EWR is a major United hub so you might succeed with an argument that they did not do everything possible to get you out earlier by switching to another aircraft.
Lots of MR / cheap fare discussed on FT involve separate PNRs and there is plenty of advice about avoiding that if possible because of potential misconnects and the loss of the later part of the trip. Same principle with the hotel no show.
As many others have said - that's what travel insurance is for. Anything from UA or Hilton will be purely on a goodwill basis - elite status might help here.

tom911

I, along with a set of friends, had a prepaid booking in Boston on Presidents Weekend and only made it as far as Philadelphia the first night due to weather and rerouting. We called both the travel provider (AA in this case, booked on their website) and the hotel (a Hilton product) and neither would budge on refunding night 1 of a 3 night stay, though the AA folks said to send an e-mail to customer service after our stay and we might have a shot at a refund. Hotel told us that booking was made through a third party and they could not touch it, and in fact had checked us in the next morning, before our arrival for day 2, so we would not lose the booking.

I figured we were out the cost of the Boston hotel for the first night and just wrote it off. My friends e-mailed AA after our stay (they had booked for all of us), and it was forwarded over to whoever handles hotel issues on their website. They verified the weather delay, contacted the hotel, and the hotel agreed to refund the first night for all of us. Certainly something I wasn't expecting.

Unrelated to that issue, I've had Hyatt cancel for me before with weather delays without any issues.

Centipede100

The passenger would NOT be covered under 261/2004 on a United flight travelling from the US to London, only if they were departing from London.

From the Reg:

Article 3

Scope

1. This Regulation shall apply:

(a) to passengers departing from an airport located in the territory of a Member State to which the Treaty applies;

(b) to passengers departing from an airport located in a third country to an airport situated in the territory of a Member State to which the Treaty applies, unless they received benefits or compensation and were given assistance in that third country, if the operating air carrier of the flight concerned is a Community carrier.

Flying Machine

Here is a cut and paste from the UA Explorer Card Travel Benefits. Seems you may be confused about the Weather/Illness. It should have been covered in OP case:

Trip Delay Reimbursement
If your common carrier travel is delayed more than 12 hours or requires an overnight stay, you and your family are covered for unreimbursed expenses made with your MileagePlus Explorer Card, such as meals and lodging, up to $500 per ticket.

Trip Cancellation/Trip Interruption Insurance
If your trip is canceled or cut short by sickness, severe weather and other covered situations, you can be reimbursed up to $10,000 for your pre-paid, non-refundable travel expenses made with your MileagePlus Explorer Card, including passenger fares, tours, and hotels.

Complete Link Here:
https://www.chase.com/online/Credit-...ection-new.htm

Safe Travels