In the book "Soldat" the writer overheard a conversation where someone said that Hitler was a gambler and gamblers won't quit until they lose. That was before even the reclaimation of Sudentenland. Prophetic words indeed for he did eventually overplay his hand and Germany (and the world) came to grief.
When the Allies attacked Germany, they faced but a small fraction of the German Army, most of which were deployed at the eastern front against the advancing Russians. Imagine if they weren't engaged in a second front and were fresh and fully deployed at the western front (and led by von Rundstedt AND Rommel, two of their finest commanders).
And without England as a forward base, there would be no way the Allies could hit at the german industrial heartlands. Coming in through Africa, the allies would not been able to conduct a bombing campaign of such a scale and of such effectiveness. It was a fact that the combat effectiveness of the german army was hampered by a serious lack of fuel. This was so bad that when the counterattack at the Ardennes was launched, the german units needed to capture the Allies' fuel dumps just to keep going (maybe they should have invented the Flintstones tank, no need fuel, just feet power ).
And not just that, air power was a significant edge that the allies possessed and was the deciding factor in many ground encounters. For example, the Allies landing at Normandy were facing a dug-in combat hardened force that was familiar with the terrain and well equiped to fight in the hedgerows. Without the close-air support of the Typhoons and Hurricanes and a bevy of heavier bombers, it could have been quite disastrous.
And i wonder how far behind they actually were in the nuclear race. They did have some heavy water processing plants so i guess they were working on fusion bombs rather than fission? Dunno anything about that. The V-1s and V-2s would make terrifying delivery vehicles though.