What if Hawai'i was Inherited by the Japanese Imperial Family?
This "what if" scenario has always been tantalizing for me:
In 1881, King Kalakaua of Hawai'i attempted to arrange an international marriage for his niece and eventual heir, the Crown Princess Victoria Ka'iulani Cleghorn (daughter of Princess Likelike). His choice was the Japanese Prince Higashifushimi Yorihito. The arrangement didn't work out, as the prince was previously engaged in Japan, but Queen Liliuokalani later suggested that her niece as crown princess marry his half brother, Prince Komatsu Akihito.
Although Crown Princess Ka'iulani never married and died at the age of 23 following the annexation of her kingdom to the United States, it is interesting to consider how different history might have been had one of the Japanese matches come to fruition.
This would have meant that the Kingdom of Hawai'i would eventually have been inherited by members of the Japanese Imperial House of Fushimi no miya (via one of the dynastic Shinnoke branches). Presumably this would have lead the Japanese Empire to safeguard its succession rights in Hawai'i, disallowing the small number of American businessmen to seize control of the government and overthrow the Hawai'ian monarchy. This scenario would also have had profound impact on the subsequent history of the United States and Pacific: either the inevitable conflict between these two empires might have occurred several decades earlier in the 1890s, or the conflict that brought the Americans into WWII never might have occurred at all.