How would the Roman Empire be formed in North America with a POD after the Columbian Exchange?

We're supposed to get a Global Empire level based on the environment of the place, not something based on the historical events of the place. Also assume that Europe and Asia collapsed after the Black Death, and only the native civilizations were left in North America. Lastly, ignore the effects of disease on the native populations, or consider them a native population. <br><br>Would the geography of North America be more akin to China or Rome?