Do I need any documents other than a valid passport to travel from the United States to London Englad by plane?

You have the required documents.

Passport is not an ENTRY ticket.

Officials at Airport will decide if you can pass.

They expect a REASONABLE travel plan.

A reasonable way to finance your plan.

A reasonable EXIT from the country. (Most have an outbound ticket to somewhere)

When returning to USA you will do US Immigration and Customs BEFORE you board in Dublin. allow some extra time for this.HINT do not have a short connection time.

Drivers License is adequate for bar ID for age.Keep passport secure at all times.

No. Assuming it is a US passport, the UK does not require US citizens to get a visa for a stay of up to 6 months.

I can add a few hints, though. At passport control, the immigration officer will quiz you about your visit, and it will help to have proof that you have a return flight booked, and enough money to cover you for that time. What they're mostly interested in is that you will leave when you say you will, and you won't try to illegally get a job. That's the reason for suggesting those. Have all that in whatever bag you will take on the flight with you, because you get to passport control BEFORE you get to baggage reclaim, so packing it in checked luggage is the wrong place to put it! Of course don't pack your passport either for the same reason - would you believe some people do? It needs to be on your person.

Nobody will be interested in your driving licence. You have your passport.

Hopefully the officer will just think you're a normal tourist and not actually ask to see any of this, but it's good to have it in case they ask.

Also take a pen because UK landing cards will be handed out on the plane and you need to fill one in. It asks for the address you are staying at so take a note of that too. You hand that over with your passport at passport control. (You'll need the pen again for filling out the US Customs form on the way home.)

Finally, a word about Customs. At British international airports, after you've got past the immigration officer (who will stamp your passport to show how long you're allowed in for), and baggage reclaim, you will come across three coloured exits. Blue is for people coming from the EU only, green is for if you don't have anything you shouldn't have with you, and red is if you have more than your duty-free limits. So assuming you don't have anything you shouldn't have, just walk through green, and almost certainly you won't be stopped. British customs officers have their own ways of deciding who looks suspicious and they're pretty good at it.

Dublin is not a problem either - you won't need a transit visa.

No, that should be OK.