Sure, issue is, if OP math checks out, currently everyone already voluntarily agrees to international law - ITU coordinating LEO orbits that extends to 2000km, meaning hard to clean >400km orbits is going to be filled with 100,000+ megaconstation hardware in next decades, substantially increasing chance of kessler. Op propose limiting >400km orbits... which means US is going to be unhappy sharing space with PRC megaconstellations. PRC not going to accept limiting >400km orbits without openning more <400km orbits because it means ceding advantage to US who locked in high% of <400km orbits since US grabbed megaconstellation spots earlier. So either everyone shares / free for alls <400km orbits, or everyone suffers Kessler, in which case whoever has the most space hardware might end up losing the most.
Sure, issue is, if OP math checks out, currently everyone already voluntarily agrees to international law - ITU coordinating LEO orbits that extends to 2000km, meaning hard to clean >400km orbits is going to be filled with 100,000+ megaconstation hardware in next decades, substantially increasing chance of kessler. Op propose limiting >400km orbits... which means US is going to be unhappy sharing space with PRC megaconstellations. PRC not going to accept limiting >400km orbits without openning more <400km orbits because it means ceding advantage to US who locked in high% of <400km orbits since US grabbed megaconstellation spots earlier. So either everyone shares / free for alls <400km orbits, or everyone suffers Kessler, in which case whoever has the most space hardware might end up losing the most.