The presence of a white squirrel wouldn't really have any long term effect on the squirrel population the forest in Florida. The reason for that is that the white squirrel, probably an albino, would have huge problems in its survival. The chances are very big that it will not be able to reach adulthood, and even if it did, it will be a short-lasting one.
The short life span of the white squirrel will be due to its coloration, which will leave it without camouflage in the forest, thus making it an easy target for the predators. Also, the white squirrel, if it somehow manages to get to stage in its life to mate, it will be avoided by the other squirrels because it has a disadvantageous feature.