I think "The Axis Powers could have won World War II" arguments in general annoy me. Germany, Japan and Italy combined barely matched a quarter (at best!) of the industrial might of the US, USSR, the British Empire and the rest of the Allies. That is me being extremely generous. They had nowhere near the same population numbers, or access to the same resources, and due to the way they ran their regimes they were extremely self defeating. Yes, the Soviet Union was a tyrannical regime itself but the difference is, they had the numbers and resource advantage and they didn't piss the rest of the Allies off.
Oh certainly, with smarter leadership and more investment in defenses and better strategies, (and if they were luckier) they could have stretched World War II on for longer. But the simple fact of the matter is, Hitler was beaten the moment he pissed off the USSR, and was definitely screwed when the Allies landed in Italy and France. Japan for that matter didn't make the Pacific War easy for the Americans at any point-They could have regained some offensive momentum if they'd managed to capitalize on the Guadacanal campaign and sinking the USS Hornet, for instance, after Midway. But in the long run, the Axis powers were up against the most powerful and most industrialized nations on the planet (ALL of whom they had pissed off) and they couldn't really support each other. They were going to lose, whether it took six years or ten years of global conflict.