Why was Henry VIII important to the Middle Ages?

Henry VIII was an important transitional figure between the Middle Ages and the early modern period. In some respects, he helped to bring the Middle Ages to a close. He did this primarily by challenging the temporal and spiritual power of the Catholic Church. Though initially hostile to the Reformation, Henry subsequently defied the Church as it refused to grant him a divorce from his first wife, Catherine of Aragon. Although what became known as the Henrician Reformation in England wasn't as theologically radical as similar movements on the continent, it did nonetheless represent a major shift in the balance of power between secular and religious authorities in Europe.
Henry's break with Rome enshrined a principle that was to become important throughout Europe, and not just in Protestant countries: the ruler of a given territory had the right to determine the religious affiliations of his or her subjects. In England, Henry made himself Supreme Head of the national Church. Among other things, this gave him the right to confiscate Church lands and wealth, to decide what religious doctrines could be taught and preached, and to authorize the publication of the only Bible permitted to be read by his subjects, the so-called Great Bible of 1539.
Henry can also be seen as an important figure in the rise of what would later become known as nationalism. The founding of the Church of England was an important assertion of English national identity. This helped to contribute to the fracturing of what the Middle Ages understood as Christendom—a cultural, political and religious unity in Western Europe that had existed for centuries.
Henry's estrangement from the Catholic Church helped to establish the nation state as the primary unit of political sovereignty. Integral to this development was the increased prominence and prestige of the vernacular, which gradually began to replace Latin as the lingua franca, or common language, of learning, especially in relation to Bible translations. In fact, the Great Bible of 1539, authorized as we've already seen by Henry VIII himself, was the first such edition to be written in English, drawing extensively on the work of the renowned biblical scholar (and executed heretic) William Tyndale.