Hypereon
He was a Consul of Rome!
If you find some, let me know Incidentally, without outsider intervention, there probably wouldn't be that much difference - technology is spurred by need, and the greatest need comes as a result of warfare, which seemed to be lacking on any comparable scale in North America.
Considering this, that's why adding different research speed for different cultures wouldn't be historically accurate at all - the people aren't any dumber anywhere in the world (or that is what it's supposed to be ). Instead - research was driven by competition and cooperation between civilizations and made possible by a high level of specialization of a large population. In other words - a small population just couldn't consider organized researching if there was just enough people to gather the food. I think this is done quite well by Firaxis with their 'specialists' that small cities can't really support.
According to The Human Web. A Bird's-Eye View of World History (William McNeill and J. R. McNeill), if I correctly remember, the main reason why Eurasia developed way faster than the Americas and Asia is the difference in cooperation and connections between peoples. Contrary to Eurasia, which is a long continent on West-East axis, Africa and the Americas' length is in North-South axis. Climate and terrain changes on this axis make traveling between far different latitudes very slow and hard, if not impossible. Thus, the civilizations in Africa and the Americas were almost completely isolated from each other, so there were little competition and contacts between peoples. Contrary, climate east-westwise does not vary hardly at all. So, links between Eastern and Western cultures from the ancient times gave Eurasia quite a head start in development.
To not completely drive this off topic, in this mod, would there be a reason to implement research boost from contacts/trade between different culture groups and raise the significance of cooperation in research? Giving some culture groups penalties to research in the future (if it's going to happen) just doesn't feel right... At least the speed of development should be driven harder by circumstances, not just from building different science buildings or from penalties for culture groups.
The optimal result from this kind of a mod for me would be seeing technology level in certain regions much more unified. Like this, we could get a certain historical situation where Continent/Region A is just starting colonizing in the Renaissance era, meanwhile Continent B hasn't still even got to the Medieval and is much inferior militarily to their fellow Continent A. It's just distracting to see some Renaissance civs in between of a couple of Modern civs, like they hadn't heard of the technologies of their neighbors at all!