Captain America wakes up and the Nazis won World War II. The way they get around this being a “What If?” story is that it’s our 616 Steve Rogers transported into the body of an alternate Earth Captain America.
He leads the people of that reality to revolution, including Peter Parker, Ben Grimm, and others.
Fun story, and at this time there’s no “What If?” ongoing series so it’s a nice use of the Marvel Knights brand.