Since we're talking about population, urbanisation and the US/Europe....
how will adgricultural production be modelled?
European (western mostly) agricultural production per hectare was much larger than that of the US (well into the second half of the 20th century iirc) although total production of both areas were more or less the same (with the US taking the lead at the early 20th iirc):
the reason for this is available landarea:
The US was, by all means, empty compared to Europe so internal colonisation and development was much more profitable in the US (expansion of arable land). Europe on the other hand had been more or less full for centuries so internal colonisation wasn't an option (hence emigration out of Europe) resulting in technology and methods that allowed for improved yields (expansion of efficiency/ha).
This affects technology in other terrains too: the US, where large farms were the norm, was a lot quicker to switch to mechanical tools like tractors for agriculture whereas Europe lagged in that field for long (only catching up post-gametime)
(hm, hope this makes sense)
So gamewise I image efficient agricultural techniques should allow European nations to sustain a quickly increasing population (which in turn fuel city growth, industrial growth, tec.), whereas the expansive US territories (Trek West, internal colonisation) should allow the US to feed its exponentially growing population (more through immigration than anything else) and cities