It's entirely possible that once Gibraltar fell, which it inevitably would, and the British were practically locked out of the Mediterranean, the Axis could probably have advanced into the Middle East after taking Egypt. It all butterflies from then on, because if you give Hitler access to Middle Eastern oil, he doesn't need to focus so much of his forces on the Caucasus, and perhaps concentrates enough extra forces on Stalingrad to win. Then Stalin goes into a rage over the loss of his namesake city, purges his military of defeatists that he blames for the loss, and this trashes the Red Army allowing for the defeat and annexation of the entire Soviet Union. Then Germany invades Alaska through its new Siberian territories, and... well, perhaps this particular butterfly has run its course.