Mongolia can be TTL's Russia
In all seriousness, you could make quite a few analogues in such a way. Japan could be like Great Britain (the Ainu representing the Celtic peoples of the islands), China would have to represent the Holy Roman Empire, or the Spanish Empire. Korea could be like Scandinavia. Thailand/ Siam could be like France maybe. India would be like the Mediterranean world (Greece, Italy, etc.)
So, assuming this means Eastern powers successfully colonized the Americas, this would also insinuate that they have outposts throughout the Pacific. Hawaii and Polynesia could be quite important. Australia, New Zealand, and New Guinea could also be colonized, and actually probably would be before the Americas would be. It's not hard, actually, to imagine the indigenous peoples of these lands falling into the same terrible fate that of slavery that African peoples did with Europeans. Although, I don't know about disease resistance, so maybe not. Once landed on the Pacific Coast of the Americas, the benefits, I think, would actually seem more obvious than it would have on the Atlantic. There's gold in California and in the Andes. The Inca would be valuable trade partners, and the Pacific coast, specifically California, is very fertile and has a very agreeable climate. The Pacific NW is rich with raw materials worth trading.
The riches from exploiting these lands would pour in, and before long Eastern kingdoms will have secured their futures as premier powers in the foreseeable future. Perhaps, eventually, these Asian countries will begin colonizing and exploiting Africa and parts of Europe for their gains.