You wanna know how Germany could have won WW2? Here's how:
It's June 1941, France has just surrendered. Don't bother with the Battle of Britain, and don't attempt Sea Lion. Yeah, it may have been possible, but it's too risky in any case. Don't worry about the USSR yet either; first you need to get the UK to make peace. Priority #1: Straits of Gibraltar. Not to gain passage to the Med, but to deny it to the Brits. To hell with The Rock, let the Brits keep it. Instead demand Petain allow military access through Algeria, waltz into Morocco, and set up a base in Tangiers. Got a problem with it, Franco? What're ya gonna do about it? So you fill it with big ass guns, the works, basically turn it into Anti-Gibraltar. Suddenly it's a million times harder to supply Malta, so you nab that next, easy peasy. After that, put Rommel in North Africa, only give him something to REALLY work with. Like, we're talkin' four panzer divisions or more. In to time, bam, Suez is yours. Brits not done yet? Cruise up into the Levant. It's not like they can stop you at this point. From there, you can establish a border to the Caucasus, which will keep Stalin honest. Brits still not done? Threaten India. GG, UK, they're not gonna keep the war going if it means risking the crown jewel of the Empire. Once UK peaces out, there's approximately zero chance of intervention from the US. Let Petain have the rest of Metropolitan France, but keep the Atlantic Wall strong, just in case. Wait a few years, get all the butter out of the German economy, and start building tanks, I mean REAL tanks, Panther quality shit or better. A dozen divisions of stuff you know can handle the T-34 with ease. When you're ready, push straight into the Caucasus and kick Stalin in the nuts before he knows he's at war. Secure the oil fields, fortify it. Next spring, attack from eastern Europe, and push straight to Moscow. Should work.
If the Japs bomb Pearl Harbor, don't declare war on the US, that's dumb. Instead, condemn the attack, break the alliance off, and let the US destroy them.
Any questions?