There are probably many ways to achieve this. Perhaps England stays Catholic for longer than it did, or maybe the French-Scottish alliance holds. Perhaps the English Civil War becomes a protracted conflict in which Scotland manages to stay a monarchy while England eventually becomes a true republic. Whatever scenario leads to this disunion, countries like France, Spain, and China would probably end up benefiting. Would this hypothetical English empire be much smaller than the British Empire ended up being? Would Scotland manage to become an independent power, perhaps integrating Ireland in the 19th century?