Throw realism to the wind! Ignore those pesky details and facts and diseases! Play down the natural advantages of Asia! Explore your Euro-wank!
But most importantly, create an analogue to the Union of the Middle Continent if those pesky pale-skins had vassalized all of it, as opposed to Asia! No petty dystopia's, please, though you can wank the height of the last unified China if it makes you feel better.
But the whatever else you do, the UMC analogue should be similar to its reputation and rhetoric of OTL: a land of gold and wealth and opportunity, a place where the oppressed masses can travel beyond the yoke of the Old Continent and gain riches by their own hard work, the beacon of liberation, and where liberty and popular consent guide the ever-changing leadership.
Bonus points if you can provide an analogue to the collapse of unified China's early monopoly on the continents, provide a reasonable Eastern-seaboard oriented holdup to simulate the initial barriers of passing the Great American Desert from the Western direction of OTL, and, of course, the Eastern Rebellion of a century and a half ago.
Think you're up for the job?