Why Singapore's fall divided the Allied naval war

Could the Pacific have operated as a more joint British-American theater from the beginning of the Second World War?

A surviving Singapore could have supported a much more joint campaign. Its loss separated the Pacific theater from Britain's major commitments in the Indian Ocean and Southeast Asia.

If Singapore had remained available, Anglo-American operations could have been much more closely integrated. Its loss left distinct Pacific and Indian Ocean campaigns, with substantial fighting in Burma and the rest of Southeast Asia. Those campaigns tied down Japanese Army forces and affected what Japan could commit elsewhere. Their limited visibility in popular accounts can obscure that connection: the criticism here applies to British histories as well as American ones.