A map of East Asia around 1900 in a world where Japan's Meiji Restoration failed to modernise the country, leaving it open to European domination, à la China. This also means that Korea and Taiwan (Formosa) - colonised by Japan in our world - are incorporated into the European system as well.
Didn't the Americans want some ports and have a treaty with Korea?
I made this quite a while ago so I can't remember my exact reasoning. I'd say some of the treaty ports in Japan are American and Americans have access to China and Japan the same as the Europeans do. TBH I think I over looked Korea a bit.
Now there's a what if I never thought of. Nice one.