Why not call this place "Skull Island" and have a ship called the Venture with movie crew in the 1930s explore this island and bring back a giant ape to Manhattan, which then breaks loose and rampages through the city, climbs the Empire State building and is shot down by National Guard biplanes? Yes, I've seen that movie, and its called King Kong. I think the story of King Kong can be called Alternate History, whats interesting is the book published afterwards about the flora and fauna of Skull Island and how that island sinks beneath the waves sometime in the late 1940s to conform that timeline to our own.
I just don't see the need of the authors for conforming their own imaginary past to our own history, why don't they just let the butterflies take effect and let the fact of Skull Islands discovery do what it will to the history books of that timeline?
A similar effect occured with a television series called War of the Worlds, this was a sequel of the 1950s movie by George Pal, but the writers of the TV series had to mysteriously make the entire population mysteriously forget the entire invasion of all those war machines, so they can come from a world similar to ours - I just don't get this mysterious adversion to alternate history and why they always feel they have to make that "square peg fit in that round hole".
Obviously a world where the Martians did invade in the 1950s and then died of Eartly germs would be a different one from the one we live in today, I don't understand this comformalism. Would anyone care to speculate why this line of story writing it so popular, that they have to make whatever fictional event fit in with our own past no matter how big it is?