I kind of stole this from one of the other threads, but my idea as follows:
In this TL, the British and the Japanese have a strong alliance. They signed the agreement some time before WWI, and Japan plays a more important part in WWI fighting against Germany. For a reason yet decided, the USA and the UK are not as chummy as they are OTL.
In this alternate TL, what would the easiest/best/most interesting way to get Japan and the USA to declare war on each other, thus forcing the UK to declare war on the US? What would the war look like? How would it be fought? Who would win?