It's useful for the MRBMs/IRBMs out of Iran targeting Europe. It's useless for the ICBMs out of Russia targeting the United States. It's not destabilizing in any way, especially since the magazine size of the Aegis sites is easily verifiable via any number of means, and the easiest countermeasure is N+! (which the Russians have in spades).
so... why is it there then? just curious. I think the official publicly touted reason at the time was to protect Romania from Iran, is that it?