The Kirk is the name for the national Church of Scotland. It came out of the Scottish Reformation, and as such represented a break with Rome and the political allegiances to Rome. Now, I realize that this is contrary to the nature of the Declaration of Arbroath, which affirmed Scotland's Independence in the form of an appeal by the nobles of Scotland to Rome for help if such could be had and were needed, but in a similar light, the formation of the Kirk represented and affirmed once again, the national independence of Scotland, and it was not until 1706/1707 that Scotland formed a union with England in what is known today as the UK (not yet including Ireland).
My point being, that even though both England and Scotland moved toward protestantism at the time of the reformation, that Scotland was still competitively independent as a result of its break with Rome (independence from Papal control) and in its own right with respect to England. England eventually won out in the form of a union, but that was not until 1706/1707, and after Scotland had made its own attempts at economic expansion through colonial imperialism in the new world. These attempts at colonies, while brave on the part of the Scottish people, turned out failures (brave because of the money the common people gave money to the company responsible for the colonies - 400,000.00 pounds - the equivalent of one fifth of the wealth of Scotland!). It was after the failure of the Darien Scheme, and the 'bank was broken' that Scotland acceded to the 1706/1707 Acts of Parliament.
Now, I haven't finished the book, like I said, but my impression thus far is that the Kirk itself was the central most culturally efficacious institution through which Scotland influenced the world. I have no evidence until finishing the book - but thus far I am convinced, and if not for the book's sake, for my own American family's insistence on the Presbyterian church (the Kirk was the origin of Presbyterianism as I understand) as being an important familial Scottish tradition. I don't claim to understand it, and in fact, am a Christian as well as an American of chiefly Scottish ancestry who accepts good people from all walks of the Christian faith as valid, but I have as well noticed the tradition of pipes at weddings here in the states, performed at Presbyterian churches, often with names like St. Andrews, etc. In fact, there is even a St. Andrews Society, and in Duneden Florida, one of the oldest Scottish settlements in the US, there is an ancient church called - guess what - 'The Kirk.'
Its prevalence is pervasive.

And so is Soctland's
Mark