The ISS orbits at an altitude of 320-347 km. The DXCC rules specify that an island is a separate DXCC entitity if it is separated from other land masses by more than 350 km. Water is not the same as atmosphere and space, but the ARRL might be inclined to apply the same separation rule to the ISS, meaning that the ISS does not qualify as a separate DXCC entity.
I have a confirmed voice contact with the ISS, so I wish that ham stations in space would qualify as a separate DXCC entity. But there are very practical reasons why the ARRL should never grant an orbiting ham station status as a separate DXCC entity. If it happens, it would be virtually impossible for anybody to make a contact with the ISS. Thousands of well-equipped and very determined top DXers would suddenly be competing to make a contact. AMSAT would be wasting its time petitioning the ARRL to grant the ISS status as a DXCC entity.
But I think AMSAT could prevail upon the ARRL to allow ISS digipeater and crossband repeater contacts (between two earth stations) to qualify as satellite contacts. ARRL is correct in categorizing voice contacts with astronauts as equivalent to aeronautical/maritime mobile contacts which do not qualify for any DXCC entity.
Wayne Estes W9AE Oakland, Oregon, USA, CN83ik