We have one, but intercepting long range missiles is very hard. https://en.wikipedia.org/wiki/Ground-Based_Midcourse_Defense https://en.wikipedia.org/wiki/Grou

We have one, but intercepting long range missiles is very hard. https://en.wikipedia.org/wiki/Ground-Based_Midcourse_Defense https://en.wikipedia.org/wiki/Ground-Based_Midcourse_Defense There are also lots of political issues around weaponizing space and deploying interceptors where we would need them. The US had to withdraw from a treaty with Russia in order to build the current system: https://en.wikipedia.org/wiki/Anti-Ballistic_Missile_Treaty https://en.wikipedia.org/wiki/Anti-Ballistic_Missile_Treaty