[freehunter]

Last time I checked, Iron Dome was only 90% effective and only had a range of 70km. The area that is constantly lobbing missiles at them is very small and easy to cover with overlapping missile defense systems. It'd be much harder and more expensive to cover Japan, and Japan is super tiny compared to many other countries that are targets for NK missiles (like the US).

It's really hard because of the massive amount of area you need to cover with a system that's basically like shooting a bullet out of the air with another bullet.