If Nazi Germany wasn't stopped we would be living in Man in the high castle world where japanese empire rule over asia, Italy over afrika and germany over all the rest with split of americas. It is potentially peaceful and safe world. Just not nice.
If you’re interested in geopolitics reading outside of Philip K. Dick, an accessible but satiating piece I always recommend is World Order: https://www.goodreads.com/book/show/20821140
It’s written by a highly respected war criminal (how many fields can say that!)