What were the key changes? I'd guess it was the defeat of the Dutch and then the French that put England on it's 180 year run at the top of the leagues (and it was THE superpower for 103 years from the defeat of Napoleon until the end of WWI.
England?.
It ceased to be England in 1707. And if any part of the UK punched above its weight, it was the Scots. From the mid 18th C to the end of Empire, it was a British Empire essentially run by the Scots.
Britain was THE superpower from 1763 to 1940.
I would therefore argue 177 years, not 103.
The former year was the end of the Seven Years War, which cemented British superiority in North America and the Atlantic, and weakened the French at sea and on land.
Britain had more territory in 1919 than ever before, had been the major Western country in the victory of WW1, and retained its preeminent military, political and economic power until that summer of 1940.
They defeated the Spanish Armada in 1588, so they were throwing serious punches before the 1700's.