There are a total of 5 primary species across the American continent, not including the chipmunks or the groundhog variants, which also have multiple sub-species to them.
The American Black Squirrel isn't actually a pure breed species, but a gene mutation between the fox squirrel and the eastern gray squirrel. At some point the two species mixed and mated with each other and the result of this is the American black squirrel.
Technically, every single squirrel species is more or less a sub species to the originals, which is the chipmunks and the groundhogs. But as you can see on this picture, the American black squirrels have yet to be given a Latin name, to separate them from the eastern gray squirrels. The reason they don't have one yet, is because that, even if two American black squirrels mated, they can still give birth to pure fox, or eastern grays, so they could in fact have a completely mixed bag of goodies in their dreys Imagine the confusion in the parents (You cheated on me! No you did!)
Now, needless to say, that none of these squirrels are the same as the European Black or Red squirrel, as they are completely different species, but still a long lost descendant of the original rodents, the chipmunk and groundhogs.
Sciurus Vulgaris = European Red Squirrels. Ciurus Meridionalis = European Black Squirrel.
Feel free to go back yesterday post, to compare the photos and the species. The main difference is of course is the famous ear tufts, as those are exclusive to the entire northern hemispheres of Europe, including UK, Scotland, Ireland, Denmark, Norway, Sweden, Finland, Russia, Estonia, Latvia, Belarus, Poland, Germany, France, Spain, Ukraine, Hungary, Poland, China, North and South Korea and Japan. Including all the smaller countries in between.