Re the comparison with Ireland and the island of Britain. (I had to go out btw). My point was that islands of their size and population, from a geographical point of view alone - geography having implications for practicality and convenience - are an obvious 'unit'. It's a pity that the people of Ireland felt the need to put a border across their island. And it would be a pity if the people of Britain can't work together either.
North America/Canada are massive so not such a good comparison.
IMO competing with each other instead of co-operating with each other is not something to be proud of.
It is arguably more 'idealistic' or morally ambitious to keep faith with the idea of sticking with the team we already have, even though the times are tough. Not through fear of economic failure or personal disadvantage but because of a wish to continue working together for the good of the whole island like mature adults rather than squabbling children in a playground who can't get along.
However decently rUK behaves in negotiations with an independent Scotland the fact remains that the two countries will be competing with each other for trade and business, instead of co-operating with each other.