Well, this is where the debate as to whether Scots is a language is strengthened. Ulster-Scots would be a dialect of it. Another point is that many natural English speakers cannot understand Scots.
And when you look at languages such as Swedish, Norwegian & Danish, they are similar enough to make it simple for their respective speakers to understand one another, right? And they're all considered languages in their own right. While Scots differs so much regionally that some Scots speakers won't even understand other Scots speakers. My point here, is it seems that some people would define a language on geographical terms, while diversity is probably more appropriate. And even if we were to define on the basis of geography, Scotland is a country in it's own right.