Represent a magical being - let's call it "overlord" - that guides this hypothetical country "Scotland" across the centuries, directing funds and other resources towards its goals.First point: ahistorical and alternative history have, in general language but mainly in the field you drag in the discussion, the same meaning: something that didn't happen in real history - but might have. Scotland conquering England and then conquering France is ahistorical/alternative history. It is, though, garbage alternative history. Conquering Europe as Scotland as represented in game is below garbage alternative history.
Represent the struggles Scotland would have to face by conquering by force England, how it would have to appease the extremely powerful English nobility, the Parliament and the clergy; represent the difficulty in finding a landing spot for its armies, a way to provide for them and keep them full force; represent the extreme problems in fighting a war to conquer a whole nation beyond the sea; represent the general hostility this would gather in those threatened, mainly Castile, Aragon, Burgundy and the HRE; represent the desperate struggle to find a way to keep the French nobles on your side instead of being armed and flanked by the other powers, who will then join them into war against you; represent the almost-impossibility to win a war at 10-to-1 numbers beyond the sea with whole territories breaking away; and THEN, if you played like some kind of Napoleon and with real skill, THEN I will accept that it is alternative history of the good kind, because all the problems that would have popped up, popped up, and you managed to overcome them.
Before that, Scotland invading mainland Europe is ridiculous.
Then give "overlord" 400 years to conquer France.
Hmmm... now conquering France as Scotland isn't as ridiculous. After all, determined men across history have proven what a single man in the right conditions can achieve. Now imagine having such an overseer living and imposing his will for 400 years.