I have researched this stuff a lot, and I am convinced that both we and the Japanese were “played” by Winston Churchill.
The British had totally broken the Japanese naval codes.
We had only fully broken the Japanese diplomatic codes.
All evidence suggest the British kept their detailed actionable foreknowledge from the US.
Churchill needed the US in the war to save his country.
He was playing chess.
The Japanese and Americans were playing checkers.
We had partially cracked JN-25 but our understanding was still verrrry incomplete.
I share your beliefs regarding likely Brit action/non-action re: US/Pac.
The Brits were absolutely desperate and came within just maybe HOURS of losing the Battle of Britain.
If they hadnt enraged Hitler away from destoying the RAF via tempting him into The Blitz, well, today we might not much later have ended up seeing the UK and all of Europe taken over by fatalistic modernity-haters.
By winning, The West lost.
Had Winnie known ahead of time, well, he probably didn’t let on to us, I think.
Churchill was a player, he was totally focused on British interests, used every tool at his disposal to try to manipulate the US. He was bitterly frustrated by the loss of British influence after the war.