So Scotland didn’t want to leave. And Scotland didn’t unite with England until after the Scottish King took over he English throne hundreds of years after the time of William Wallace
You might be confusing the U.K. with the USA where a pet of the country there wanted to leave and were refused and that did lead to war, and that happened far more recently than 700 years ago.
And wars happened when scotland was forced to become part of the UK in medieval times. (Braveheart)