Have a united Ireland and and a united independent Scotland unite through dynastic marriage to form a Gaelic super kingdom to rival England and any other adversary in the british isles at any time between 1014 and 1500. From there, have them expand and conquer the isle of Mann, Orkney, Shetland, The Faroes, Iceland and Greenland and possibly some colonies in North America.
In the post- Colombian colonial period, the Gaels are therefore a colonial power along with the Spanish, Portuguese, French, Dutch and English.
In the post- Colombian colonial period, the Gaels are therefore a colonial power along with the Spanish, Portuguese, French, Dutch and English.
How can such a situation arise?
Who will their main rivals and enemies be?
Where will the capital be?
Will the empire stay catholic or become Protestant?
Would a Hiberno-Scottish split be on the cards?
What about other causes of instability?