Hitler's keys to victory was Gibraltar British port and Suez Canal. If he took both of them away from the British, the Mediterranean Sea would have been an "Axis Lake" and had a better ability to harass British shipping and link up with Japan. Also, Britain would have a tough time moving men and material to England.
The Axis still would not have won the war. What everyone completely ignores is that by bringing the US into active participation in the war, the Axis powers signed their death warrants. Due to the depression, the US still had tremendous slack in it's industrial capacity. In fact, we had more slack capacity than Germany, Italy, and Japan's total industrial capacity. Our total industrial potential was greater than all the rest of the world combined. Trent Telenko has documented this over at the Chicago Boys website. It makes for very interesting reading.
Hell, we put 13 million men in uniform, built the largest and most powerful Navy the world has ever seen, ~250000 military aircraft, over 50000 tanks, and enough munitions that our military was still using WW2 stockpiles 30 years later. We fed and fueled the whole world, all the while raising the standard of living at home.
Japan and Italy were stretched to the limit the moment they entered the war, and Germany was by late 1944, while the US had to cut back production in Fall 1944 because we were not going to need it. American production had just finished warming up and had not yet peaked out. If the Germans had been able to prolong the war into 1946, they would have been nuked first in August 1945.
The Axis powers were doomed from December 7, 1941 on.
