Does Karman line depend on the wing area, and if not, why? The Karman line is the altitude at that the airspeed required to generate the sufficient lift to support itself exceeds the orbital speed. Looks like the Karman line is defined as some fixed value, equal to 100 Km. How this could possibly be? 

In a usual flight, "the airspeed required to support itself" depends dramatically on the wing and can vary I think from 29 km/h for Gossamer Albatross till 389 km/h for X-15.
The calculation definitely does depend on wing loading. However, the Kármán line does not, because it is not actually defined by that calculation, it is defined by statement. The calculation, for a “typical” airplane, is just motivation for the value.