I don't think it would cause any major direc changes. Obviously there will be immense and important butterflies, but we can't really predict those.
I think the first question we need to ask is why get writing. Early writing seems to have been used mainly for the purpose of bureaucracy, trade and, religion. I think the most likely reason for widespread adoption among Native Americans of writing is the use by administration, particularly in the Mississippian basin and the Southwest, which seems to have had a more organised governmental system then their more north-easterly counterparts (I find it highly unlikely that any non agricultural group would adopt writing, so I have discounted them for this thought experiment), and I think it wold be easy to see Cahokian priest-kings using writing to plan development and extract taxes. The Southwest, with its complex systems of irrigation and cults. In the Northeast I'm not seeing the form of bureaucracy that early writing usually shows appears in, with neither the governmental or religious organization that usually would create writing. However we can probably get some form of writing even if it requires upping the level of organization in the Northeast.
Then the question becomes how they get writing. There are two scenarios, that writing spreads from Mexico northwards, or that writing gets developed independently and then gets spread. However, writing has only ever been invented independently definately three times (China, Mesopotamia, Mesoamerica,) and maybe five other times (Egypt, The Anatolian highlands, Easter Islands, the Andes, the Indus Valley), so having the independent invention seems implausible, so spreading from Mexico makes more sense.
In South America, the question comes down to whether the quipu was writing (or at least some form of information record with clearly identifiable parts that is not subject to any more interpretation then speech). If it is, then we simply need to spread it to the Colombian agriculturalists and maybe the Amazonian civilizations (if they existed). The peoples in the Carri bean can probably gain writing from mesoamerica.