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Lets say, for a scenario that the Ming in 1435 do discover the Americas but with nomajor incentive to explore the area they go along the Hegemonic Path of getting the loyalties of a few of the tribes along the western coast and contacts with the Aztecs before their defeat to Spain but as apart of a Zheng He style of setting up outposts, a Chinese 'Outpost' city mainly atuned for trade, getting tribute from the locals and harvesting of local resources is set up in the area of San Francisco Bay and over time grows slowly, mainly a area for exiling various peoples who displease the Ming and those forced off their land by debt or plague or etc and possibly see's immigration by Japanese. Spanish influence would be checkered south of California.

So come the time of the arrival of the Manchus and the Qing, Koxinga as his base in Fujian erodes travels westward and secures the most eastern of Bastions from the Qing, setting up a Ming Bastion in the Americas rather then Taiwan with its hostile natives and annoying Dutch. At the sametime this outpost will recieve population of refugees from the Qing and swell up in size, and for sometime likely remain out of the Qing's grasp while their naval skills are inadequate to invade across thousands of miles of ocean.
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