The administration is serious about Golden Dome (as was Regan with SDI). We'll see what happens when the democrats return to power.
There are three phases of flight in which an incoming missile can be engaged - launch, mid-course, and terminal. Israel's Iron Dome is a terminal phase intercept solution designed to knock out rather slow, free flight, short range rockets used by HAMAS and Hezbolah. It is useless against long range true ballistic missiles like Iran uses. For these, the IDF employs their Archer and David's Sling systems that are analogues to US Patriot and THAAD.
These terminal phase systems are effective in point defense against conventional warheads. They are not of much use for area defense, and detonating a 1.5 megaton nuclear weapon a mile or two from its intended target isn't a particularly useful strategy.
Launch phase is difficult to attack unless the target country is somewhere like North Korea where its missile launches would be very near interceptors. It is one reason Aegis has been continually upgraded to engage these sorts of targets from just offshore North Korea. However such technology is of limited value against Russian and Chinese missile fields and launch points far from the ocean or national borders.
That leaves mid-course. These engagements would take place beyond the atmosphere and ideally before the warhead has time to deploy its independently targeted payload and decoys. In spite of intermittent funding, the Missile Defense Agency has made a lot of progress in this capability over the last twenty years. In 2023, MDA demonstrated a successful mid-course intercept by its Ground Based Mid Course Defense System (GMD) employing its Exoatmospheric Kill Vehicle (EKV) developed by my old corporation and now built by RTX. My old company is now leading the glide phase intercept effort for hypersonics.
Virtually all ballistic threats approaching the United States from Russia or China will come over the Arctic. For any ground based defensive system capable of reacting in time to intercept those targets outside the atmosphere, that makes geography like, Alaska, Canada, and yes, potentially Greenland very important for both target acquisition and engagement.
Due to the emerging challenge of hypersonics, the eventual Golden Dome will require a layered defense and almost certainly an orbital-based capability as well. The point is that this program is not having to start from a clean slate, and the administration has clearly been made aware of the limitations of a purely US -based system.
