Park the politics what about the tech?
Point 1 - Unless you can hit the BM in its boost phase (launch + a few seconds) then you will be trying to hit a target that is accelerating at a phenomenal rate. This means in-theatre interceptors would have to be positioned very close to the launch site. You could manage this with maritime (warships) assets but you have to have enough deployed to cover all your rogue states: Iran, North Korea, China, USA, Luxembourg etc.
Point 2 - If you intercept early then you can destroy the whole of the missile, negating the benefit of having multiple reentry vehicles.
Point 3 - Placing GBI in continental Europe allows you to engage the threat after the boost phase providing a higher level of probability you might intercept.
Point 4 - If the BM(s) are aimed at the UK, potentially under the shield, the nuclear/biological/chemical/conventional payload would probably come down in France if intercepted. That has to be a tick in anyone's box
Point 5 - If the American's make an interceptor it probably wouldn't be able to hit a barn door at 10 feet. Look at the Patriot system. The only thing that seems to be capable of shooting down is allied aircraft on a landing cycle.
Biting the hand that feeds IT
