In any protracted conflict the U.S. would have been the inevitable winner. It's tough to say what the fleets would have looked like had there been no Washington treaty, but there's no question that the U.S. could have outproduced the U.K. many times over and eventually enforced a successful blockade.
Remember, in this time period, industrial production of both countries was relatively close. If the war dragged on 5 or 10 years, the gap accelerates, but I wouldn't think that likely. A one or two year campaign, perhaps, before both countries come to their senses?
The really fanciful consideration is always that Britain harnesses the manpower of Empire, then convinces both Canada and Mexico to invade - then the US is facing enemies from potentially all four sides and invasion becomes possible.
Of course, you have to ask, what happens then? Let's say those forces defeat any serious army on US soil. Whoppee. For all the good it would do them
The big question would have been how did that war influence the entry of the U.S. into WW2 against Germany? Would it have delayed it? Would there have been resistance to helping the UK at all if there was a lot of residual bitterness? Might the Axis have attempted to include the U.S., or at least reach some settlement with it? If there was no help for the UK, would Germany have eventually conquered all of Europe and then possibly developed the first a-bomb if the U.S. hadn't been forced to?
Big questions indeed. I would go with yes, yes, no (nothing that could be trusted once Russia was dealt with anyway), and yes
Or would a surge in prestige in the 30s have caused the U.S. to have greater imperialist posture in the Pacific, possibly averting Pearl Harbor and forcing the Japanese to come to a negotiated arrangement instead?
The normal answer to that is normally some murmurings about isolationism. That is possible.
A US empire? An interesting idea, but I think it would have run smack into a rapidly expanding German one who would have control of the seas by virtue of taking over British bases and various overseas possessions.
Of course, Hitler would probably then do something to cock things up
Countless different ways things could have played out. . . but that was such a pivotal point in world history that a British-U.S. war at that time, while maybe not causing a huge disruption in itself, would have definitely cause a chain of events that left the world looking very different than the way it does today.
Indeed. Always fun speculating
On the other hand, history has a habit of coming up with events no one could possible imagine..