15 May 1940, Churchill suggested that the U.S. Navy use Britain’s Singapore base “in any way convenient,” hoping to keep “that Japanese dog quiet.”
What would have been the impact if FDR took up Churchill's offer? Certainly, FDR isn't going to send his battlefleet and carriers to Singapore. If they're leaving Haiwaian waters to rattle the Japanese they'd be going to the Philippines.
But after Japan seized FIC in Sept. 1940, FDR decides he'd better send something. The USN sends six cruisers, ten destroyers, and a dozen submarines to Singapore in November 1940, permanently basing them at Singapore until further notice.