there's two big flaws in that.
1. the Germans could never have invaded Britain because they didn't have the naval capability to lift troops across the Channel and they couldn't mount an air-only invasion without destroying the RAF and they singularly failed to do that in our reality and any attempt at a sea-borne invasion without air dominance over the channel would've left the ReichsMarine at the bottom of the sea, even without factoring in the Royal Navy's capacity to whup ass.
2. the Japanese couldn't have invaded Hawaii because they lacked the fleet capacity to get that far across the Pacific with enough troops.
so, i know what you're going to say: oh, but given enough time they could've built more ships.
nah, the Germans would've had the British bombing the shit out of every port and shipyard going and the Americans would've woken up and smelled the sake before the Japanese got a big enough fleet and whupped ass too, assuming Britain and the Sovs hadn't already spanked the Germans and diverted their forces to the Pacific theatre.
oh, yeah, cuz everyone forgets that Britain had interests in the Far East and was fighting out there too. it's just that, understandably, Germany was the bigger threat. remove that and Britain goes to war on Japan.