In an alternate history I am designing, the Mayans and the Aztec start a lot earlier and become much more powerful, domesticated more animals and thus contracting plagues, These plagues spread across the Americas and destroys the population. By the time Columbus arrives, he also brings back diseases while giving them to the Natives.
In this timeline, the colonization of North America does not start until the late sixteenth century and when it does occur, it takes a lot longer. By the time the Europeans successfully colonize Oklahoma, I want Asia to begin travelling across the North Pacific and colonizing the West Coast.
What Asian nations of the sixteenth century would have had the most capacity (resources, technology, skills, personnel) to colonize the West Coast?