Angevin Empire
Randall Garrett's "Lord Darcy" series presents a point of divergence: a monk systemizes magic rather than science, so the use of foxglove to treat heart disease is regarded as superstition. Another point of divergence occurs in 1199, when Richard the Lionheart survives the Siege of Chaluz and returns to England and makes the Angevin Empire so strong that it survives into the 20th century.