How interconnected were societies before 1491?

I am assuming you are referring to Pre-Columbian societies as discussed in Charles C. Mann's book 1491. These early American societies were actually quite connected. The Aztecs controlled a great deal of central Mexico through either conquest or demanding tribute. Trade goods such as conch shells have been found in Mississippian burial mounds. Feathers from tropical birds have been found in archaeological digs in the Northeast. Even without the aid of horses, early Americans still explored their surroundings and sought out trade goods. Either through trade or diplomacy, many tribes had at least some knowledge that other cultures existed. This explains why disease killed off millions of Native Americans before they even had contact with Europeans—the trade networks which had existed for years before 1491 served to carry disease vectors across the continent when the Europeans arrived.