I don't think that's the only way. If Dunkirk and the Battle of Britain go just a little differently, Germany has air superiority over the Isles.
Dunkirk is irrelevant; Britain only deployed a token air force to the continent, so even if it had been entirely wiped out it would have made little difference. I've already discussed the Battle of Britain above; all I'll say here is that German fighters didn't have the range to even fly over the whole of the isles, let alone establish air superiority. I consider the suggestion laughable.
If the OKL and OKM weren't always feuding, perhaps they notice that a small percentage of the Luftwaffe in a small percentage of the time was accounting for a huge percentage of British shipping losses.
This is a surprise to me; I've hear of no such thing. The effectiveness of aircraft against naval targets was only really recognised after the Battle of Taranto, which was after the BoB was decided. Moreover, aircraft are in general vastly inferior to submarines for interdiction purposes; submarines can hunt undetected for months, far from any identifiable base.
Just for comparison, the US submarine force, comprising only 2% of US navy personnel, accounted for over 60% of Japanese sunk tonnage. There is no way aircraft could have remotely approached this.
Then there's the matter of where British shipping comes from. Hitler fatally started ignoring Britain once he felt they were beaten. If he takes them seriously and approves Operation Felix (seizing Gibraltar with or without Franco's help), the war in north Africa and the usefulness of the Italians drastically changes.
Well, I guess that's true, but I think only getting full Spanish entry into the war would have helped. The British demonstrably carried out several landings against fortified points in Europe and the Med; there is every reason to believe that the importance of Gibraltar would have forced them to do it there.
Even as late as 1942, if he'd sent Rommel a couple more divisions he likely takes the Suez and beyond.
Which was a course of action Rommel himself had advised against, until and unless Malta could be taken. Which it was not.
And if Japan is further "encouraged" to go after British holdings rather than American ones, you've essentially cut off British shipping at its sources rather than at its destination.
This would have been directly contrary to the Japanese war plan, which knew full well that their only hope was to smash the Americans so badly and so quickly that they could force a settlement; detaching forces to pick fights that did not contribute to this goal would never have been considered.
A lot of what iffing, but each one was a plausible event on its own.
Opinions clearly differ.