Full Spectrum Dominance US first strike planned 2016.

That missile defence isn't up to dealing with the numbers Russia or China could throw at the west if they wanted. MAD is still a very real threat if they got involved in some nuclear exchange. However it makes purchase of Russian or Chinese missile tech less worthwhile to any potential rogue actors. It's meant mostly as a deterent to countries like North Korea or Iran (and possibly Pakistan or ISIS depending on what happens) and the likely number of missiles they could field.