Hitler dun goof.
1) Invading Poland triggering Britain (Hitler did not expect for Britain to go to war against Germany over this. There was also elite in-fighting between the two nations)
2) Invading the USSR (literally suicidal to fight a major continental land power and strong artillery/rocketry).
3) Declaring war on America (still would've gotten involved in someway, but could've curtail to have bought more time).
An absolute mad man involving all of those major powers... and Italy/Mussolini was a useless ally for Hitler only Hirohito/Japan was a much more useful ally to Hitler than Italy/Mussolini.
Should've blitzkrieg to the oilfields first (they tried doing this in Baku but was kind of too late and they wasting their time on other stuff, which render their resources of the Nazis thin) and hold onto those oilfields, and to replenish supplies. Mussolini was holding back Hitler a lot. Hitler had to send his troops to North Africa and the Balkans to help Mussolini, even Hitler was getting tired, and frustrated with Mussolini lol.