And then there is the fact that even by 1941, we were still ramping up the military and we really weren’t ready to do very much then.
FDR was probably holding out for another year or two before committing. But Pearl changed all that.
Fact is, the Empire was finished, although few at the time understood that. The subjects were tired of being, well, subjects. India was so big the Brits could not hold it once the people wanted self-government. And even places like Canada, Australia and New Zealand wanted to be treated as equals, not as Imperial outposts.
British financial disarray was not due to America. The City had been bled deeply by the cost of WWI. By 1941, Britain was broke, even considering its gold reserves. Granting the US rights to bases in British possessions was the tissue that allowed Roosevelt to sell Lend-Lease to a country still dominated by isolationists. In reality, Lend-Lease was a massive foreign aid program from which the US got little monetary value in return - but did get two allies capable of fighting.