Could Asgard exist in real life?

Probably not.

One way allowed by physics to create something similar in shape to Asgard would be that of a celestial body with a pronounced flattening at the poles.

The shape of the earth is, to be exact, a spheroid or oblate ellipsoid, a rotation ellipsoid that is obtained by rotating an ellipse around its shortest axis, which in the case of the earth is represented by the one joining the two poles (since our planet is only slightly flattened at the poles, and the ellipse sweeping the ellipsoid has a low eccentricity).

If the ellipse described by the planet in question had a much more pronounced eccentricity than that of the earth (hence a much more oval cross-section), and the planet’s rotation was extremely fast along with a low density (which would further deform the planet parallel to its axis of rotation) then the shape it would assume would be almost that of a disc in which the poles would be the faces and the equator the edge.

The problem is in the density that this planet would have to have, which combined with the high number of rotations of the disc would probably tear it apart in no time. In addition to the fact that on Asgard gravity only works in one direction, whereas in reality stuff would be attracted towards the center of the disc, thus accumulating near the poles. One more reason not to believe that the Earth is flat.