Did Scotland Ever Merge with England Like Wales Did?
1707. Read your history school books again.
A Brief Historical Context
The Tudor monarchy died out, and so the royal line was traced through Henry VII, to the deceased Mary Queen of Scots, to her son, King James VI of Scotland, who inherited the English throne as King James I of England. Two countries with the same king, but the journey of unification has taken different steps.
The Welsh Path to Merger
England and Wales were formally united under the Tudors, who were themselves of Welsh descent. Henry VII and his grandfather, Owen Tudor, were both born in Wales. Although Wales had effectively been under English rule for about 200 years since Edward I's time, it was the Tudors who gave the Welsh the same rights as the English. Approximately 100 years later, Henry VIII's last descendant, his daughter Elizabeth I, died, passing the throne to her great-grandson, James VI of Scotland (who also became King James I of England).
The Evolution of Britain
It's important to understand that Great Britain, like all of Europe, was once tribal land, gradually merging willingly or through conquest into larger groupings. France, Spain, Italy, and Germany have all developed from smaller states. Italy and Germany did not exist until the 19th century.
The unification of Great Britain began in the 4th and 5th centuries when the Saxons and Angles invaded and created kingdoms larger than the tribal lands of the indigenous people. These kingdoms were eventually brought together in 927 as the new kingdom of Angleland (early form of England).
Meanwhile, the tribes in the north were gradually conquered and absorbed into Scotland. By 927, there were two areas not absorbed by Angleland or Scotland: Northumbria (between the two) and Cymru (Wales) to the west. By this time, Cymru was the last region in Britain that still spoke its own Brythonic language, which the Anglish ruling class called "Welsh," literally meaning "foreign."
In 954, Northumbria was taken by Angleland and its king was murdered. Half of Northumbria was seized by Scotland in the following years. So, most of the British were now in two kingdoms. The Cymraeg-speaking tribes in the west, known as Cymru (Wales), remained independent for 600 years before they were finally absorbed into Angleland, becoming the Principality of Wales in 1542.
England and Scotland had a fractious relationship until 1707, when the two kingdoms voted to dissolve and create the new country of Great Britain. At that time, Scotland was nearly bankrupt and needed bailing out.
The Unique Path of Wales
Wales remained part of England until 1955, when it was recognized as a separate entity within Great Britain and given its own regional capital at Cardiff. This makes the path of Wales to unification unique compared to Scotland, where the formation of the United Kingdom was a clear political decision in 1707.
So, 1600 years after Great Britain was an island with dozens of tribes, it is now one country. But the people are still quite similar: 1600 years ago, all the people of Great Britain were the same Brythonic people, and today, Britons (except for recent immigrants) are still all descended from those Brythonic tribes, with over 60% of modern British DNA still coming from that original population.