Charles I was more than the King of England; he was also King of Scotland and Ireland. Wales was a Principality which had been annexed by England through Acts of Union in 1536 and 1543, and the King of England was also the supreme ruler of Wales. It wasn't the instability of England which resulted in civil war; but the instability of three kingdoms under one King. And by the end of the 1640s, Charles had lost them all.
As King of England, Wales, Scotland and Ireland, Charles governed a multiple kingdom in which each principality had interests of its own which frequently conflicted with the others. Each nation had its own legislative assembly and executive government. Today, with a Scottish Parliament, a Welsh Assembly, and a Northern Ireland Assembly, we are seeing the same kind of political structure - one where power is not centralised in London, but is dispersed through a number of different, often competing regions.
Power rises and falls between the different centres. We are witnessing today a return to the Three Kingdoms which the seventeenth century was familiar with. The difficulty, like now, was that the powers in London were not particular fans of devolution.
The greatest difference between the three kingdoms was over religion. England muddled through with its Church of England. The Scottish Kirk held to a more rigorous version of Calvinism which downgraded the role of bishops (known as Presbyterianism because of its system of church assemblies and lay elders). And Ireland was divided between Catholic Gaelic families, Catholic 'Old English' settlers (who had been there for generations), and a new wave of Protestant English and Scottish settlers. Supporting one policy in one country could have disastrous effects on relations in another - what might be right for the Crown in Scotland could be terrible for it in Ireland. The three kingdoms operated like billiard-balls nudging and knocking each other; always aware of the actions of the others. One ball could easily smash apart the carefully laid plans of the other two.
The problem was that Charles, with his unerring belief in the wisdom of his kingship, thought he could rule the three kingdoms as one country. He had no inclination for the politics and diplomacy which were required for governing a multiple kingdom. The first to feel the brunt of his 'one country' policy was Scotland.
Scotland has never really taken to being ruled from Whitehall. The historical relationship between London and Edinburgh is marked by regular outbreaks of resentment and rivalry - this was to be one of the earliest and most successful examples. The relationship was made more fraught by the character of Charles. The Scots didn't like his haughty manner, how he ignored them at Court, and how he built up the power of the Bishops and Church in Scotland. One of Charles's first and most inept reforms in Scotland had been the Act of Revocations which returned land to the Scottish church taken by nobles at the time of the Protestant Reformation. It was, according to one observer, 'the grounds of all the mischiefs that followed after.' Hostility to the Prayer Book provided the perfect excuse to teach Charles a lesson.