The alliance counterfactual has to account for instability inside Japan and Britain's uncertainty about which Japanese political forces it would face. Britain could instead work with a more predictable United States while the Empire was already moving toward a Commonwealth relationship. The First World War, Great Depression, and Second World War then struck a trading empire whose cohesion depended on maritime flows of goods and capital. Repeated disruption to those maritime flows helps explain imperial decline more than the loss of one alliance. The comparison with the United States makes a related economic point: states that escape physical devastation can emerge from major wars in a stronger position.
Notable Point · 4:27-6:37
Alliance continuity could not by itself preserve the British Empire
Preserving the Anglo-Japanese Alliance would not necessarily have prevented the Second World War or saved the British Empire.