Would there by any pushing north up the coast of what is today the US? Whether it is out of sheer curiosity or chasing the cod fish stocks or any other reason?
The same curiosity that lead to expeditions along the Pacific could lead voyagers up the east coast. This will be peripheral to the Mississippi however, as most of the more lucrative goods would travel down river from as far as the Great Lakes (and a much greater volume as well). Imported Mesoamerican goods would also find an easier way into the interior via the Mississippi as opposed to the eastern seaboard. The northern limit of influence from the Caribbean would likely match that of the South Appalachian Mississippian culture.
However, when Florida urbanizes further, the peninsula would make excellent middlemen. The Gulf stream will take them very far and New England, for instance, would benefit from not having to deal with crossing the Appalachians for Gulf Coast goods.
As for reaching West Africa, I was wondering if any sort of long-distance trade might occur, akin to Greco-Roman trade in the Indian Ocean and with China.
If it did it would be very much the Natives initiating and maintain it. West Africa had very little of a blue water naval tradition, and its coasts were much less developed than the hinterlands (particularly around the Sahel)
Funny you mention Greco-Roman trade, because I imagine much of Circum-Caribbean would look like the "Periplus of the Erythraean Sea" if allowed to mature. A Maya periplus would be very fascinating.
I've given West Africa some thought. If no one's willing to sail from the Mediterranean to Senegal, some African specific changes could be very pronounced. I'm probably stretching things quite a bit. We are talking about very early divergences here but I'm always willing to speculate.
Bear in mind, this is a very long term projection (probably not having a solid place in this thread). Think of this as a template and launch point for other ideas rather than the inherent outcome of the POD.
For this scenario, assume that European colonialism as it occurred in the sixteenth century is suspended indefinitely. Also assume that the Maritime Age is already fully developed. Its gonna be another wall of text and I'm really, really pushing the envelope here:
With more frequent landings of wayward *Americans* on the coast of Africa an exchange of crops occurs, similar to the sweet potato's impact in the Pacific. The coastal west African societies experience a population boom and myths of boat people disseminate along the shore. Shipping technology has slowly improved (but no catamarans, alot of knowledge has been lost along the shipwrecks). Eventually, someone decides to make a return trip (perhaps similarly to Abu Bakr II's proposed voyage, or a South American whose managed to return home). The knowledge of another great land to the east, a more populous and ocean oriented coast, and the familiar foods found there encourages more to make the voyage across the Atlantic.
On the Mid Atlantic islands *American sailors dominate but on the mainland disease takes a toll. Eventually a hybrid culture forms between the islands and Western Africa. This group is what encourages trade between the two continents. They use iron and have herded cattle, and cultivate foods like African rice. Through such middle men African domesticated flora and fauna make the trip. This revolutionizes non-Amazonian Brazil, with a herding economy developing and spreading from the coast.
Tropical diseases like malaria and yellow fever spread to the Americas when trade becomes more direct (more sanitary sailing conditions on the boats helps alot i.e. tons better than a slave ship). The effects of the diseases are harmful and with a well developed trade network they spread quickly. The "Maritime Age" ends in a vaguely similar way to the Bronze Age Collapse (though in all honesty the two periods aren't that comparable, this is more a visual aid). The following period is characterized by lower but still important trade and volumes of goods as the indigenous people adapt to the changes of of their carefully managed environment. The Trans-Atlantic trade would've otherwise faded (and in most worlds would have), but the hybrid culture has managed to sustain it with their vulnerability much less than the others. This group is too small to replace the indigenous Americans and they're assimilated fully into the societies there in a manner akin to the Oorlam of Southern Africa. (They could also become something like Pochteca-Dyula traders, that would be quite the sight)
In spite of these changes, the Americas would, over many years, recover. Note that the Congo maintained a population in the millions before Leopold. ITTL the Americas still suffer from diseases but they won't suffer from mass enslavement or total displacement and forced migration. The initial population was much higher and the spread of technologies and livestock from Africa has mitigated the population decline.
The Caribbean rim, Gulf Coast, Mesoamerica, and the Andes, faced with new diseases and the introduction of new flora and fauna, change considerably. Many of the old kingdoms, chiefdoms, cities, and empires have either disappeared or were reincarnated into new societies. Diseases become endemic in the aforementioned regions but a new era dawns. Succeeding the Intermediate Era, this new period has the plants animals and technologies radiating outward. The time it takes for this to occur is similar to the Bantu Migration in Africa. It may actually occur faster as the Americas have centuries of well established connections (plus they were introduced at nearly the same time for both continents, which by themselves are smaller than Africa).
Fast forward several centuries and the Trans Atlantic diffusion is complete. The Americas have developed new cultivation and husbandry techniques. The population is higher than ever, and transportation over land is developing in a way unimaginable to the first Maya voyagers. In fact the Maya heartland and much of the Americas are developing new technologies on par with the east. Even if, after all this time, an ATL European conquistador travels to the Caribbean he'll find himself suffering from the same tropical diseases encountered in Africa and demographically displacing the indigenous population is essentially impossible. The Great Exchange, in contrast to the Columbian Exchange is much slower, initiated from the Americas, and the indigenous inhabitants have used their leverage to their advantage.
[On the Norse and the like, note that it was European contact as it occurred
in the sixteenth century that was suspended. Something like Vinland, or a deeply diverged Europe (Non Indo-European for example) isn't mutually exclusive with the scenario]
