They already had a form of unity, and not all where nomadic.
The Iroquois had founded the basics of a democratic society with other nations, as well as a general unity amongst tribes just prior to European Settlement. There would have undoubtedly been more potent forms of kingdoms and nations had they been left a century or so longer unprovoked (however, where such processes took a short period of time in Europe, the North Americans had been trying at it since before BCE and had only begun to achieve such organization literally just years before settlement).
There was some basic information sharing, however the openness of information in a society is not the major factor in technological achievement and advancement. Europe and Asia are resource-rich continents compared to North America. Had they formed nations comparable to, say, Rome, it would have taken them much longer to discover new technologies and may have limited them to a lesser variety of such technologies. This is supported through the fact that it took so long for the North Americans to achieve something that had been achieved several times over in the rest of the world.