As far as I know, Blender and Panda3D used the same coordinate system, Z-up. Something else must be wrong. Perhaps there is a negative scale component applied to the object in some way? Or some parent object has the wrong scale or rotation?
As a workaround you can call flattenLight() on the model in Panda3D to tell Panda to apply the transform to the vertices, which would essentially set the transform to identity.