As an attempt to provide a completely new form of journalism I call "Acespanlojournalism," I have done something wholly original, which is to imitate Vox, which is to further say, read a few Wikipedia articles and present them as original research.
Here then the Acesplanation. And I really have to stress this comes from Wikipedia-- this is all their work, rewritten. And I have to stress I knew nothing before reading Wikipedia, so this is non-expert and probably unreliable. (Not because Wikipedia is unreliable -- but because a non-expert digesting what are themselves digests is going to result in a superficial accounting that probably emphasizes the wrong things.)
The Scottish Wars of Independence, and Why That Has Nothing to Do With Any of This
Scotland was an independent state before the Wars for Scottish Independence depicted (inaccurately) in Braveheart, too. English control of Scotland was a fairly short-lived affair. The Scottish king, Alexander III, died, and then so did his daughter and heir at a young age, leading to a disputed succession.
Edward I -- who I'll just call "Edward Longshanks," because we all know him from Braveheart -- graciously offered to mediate the succession dispute, and came up with a terrific solution pleasing to all parties: He invaded Scotland and declared himself "Lord Paramount," overlord over whatever king should eventually take the Scottish throne.
Longshanks was depicted as the villain in Braveheart, but you gotta admit: That's a Pimp move, man.
This sparked the First and Second Wars of Scottish Independence, which were fought in rapid succession.
Ultimately, Robert the Bruce became King of Scotland and managed to drive out Edward and his pretender to the throne (a man named Edward Balloi), and Scotland was free once more.
These events are actually pretty much unconnected to the union of Scotland and England, and I only mention them to emphasize that: They're not connected. It's not as if Longshanks' forces continued to hold Scotland to the present.