The surface area of the zone that the ISS orbits would be 223,023,973 miles².

But you have to remember that all orbits will cross paths twice if they are the same altitude. That doesn’t mean that they will both be in that same spot at the same time though. To be in the same orbit they would have to be going the same speed, so in that case they would never collide if they didn’t collide on the first trip around. It would have to be debris that were pulled closer from a higher orbit by gravity. Still, a very slim chance given how large that area actually is.

The sphere including all of LEO and the Earth is over 2.4 trillion cubic km. Earth is a smidge over 1 trillion cubic km. Subtract the volume of the Earth and you have 1.4 trillion cubic km left for the 100km below the Karman Line and 1900km above it.