It wasn't that close and even if they managed to get some sort of win, they would never have been able to hold it. Mainstream media likes to portray Nazis as an efficient machine, but it turns out when you hand out promotions based on the shape of the officer's faces, you get a dysfunctional military.
There would be no way to stop. The German economy was really messed up by the Nazis. They essentially had no exports because they were producing mainly materiel for the war and were under an embargo anyway.
That means they had no way to get money besides literally taking it from conquered countries. The problem is, you can only loot once. This created a vicious cycle where they became more isolated and needed to conquer even more.
Honestly, before nukes existed, the Nazis could have been defeated by an embargo. But it would have cost more lives. Invading Germany saved lives and the nukes saved even more lives in Japan.
The Nazis had about 4 million people in uniform at the start of the war, America has about 1.5 million today, but it's not a bad comparison considering the last time American debt exceeded the GDP was the end of WW2.
Though to be fair, the U.S. has a lot more of an economy and population to work with and isn't investing nearly as much, far more was spent on the military by Germany as a percentage of their GDP, and their military had more people per capita than the U.S. does today.