well if you think about it ICBM or IRBM are proven and battle tested systems that will definately work.
No one has ever came close to building an ABM system. How many analysts have been warning that this project could turn into a massive blackhole for funds and no guarentee that it’s going to work at all… Look at how strong the US have been lobbying parters to share its burden… They are pratically forcing Canada to join in as well.
To develope a ABM infostructure you need a lot of R&D and a lot of money. This money is used in the american economy and thus stimulation it’s growth. I can understand why US would want to develope such a system but why anyone else would be suckered into paying is anyones guess.
they not going to shoot ICBM to japan because they are not that far away if ever china go nukes they going be firing a massive of amout of cruise and tactical missles liked WS1-b they very cheap to produce and mobile too a ABM system don’t address this.go ahead build your abm force