The challenge is both the production time and the high cost of such a high-tech missile. Typically, the US Navy fires two missiles at each given airborne target to guarantee its downing, and an interceptor missile costs millions of dollars, much more than the Iranian missiles it shoots down.
This was always going to be a problem and it's their fault for not moving sooner on it.
If an adversaries missiles costs a million dollars, how do you challenge them? Make missiles that costs less and overwhelm them.
Not only do you gotta worry about Iran's or others cheaper missiles, but now there's drones that are a fraction of the cost.
If the US enters a major conflict, I wouldn't be surprised to see high value assets get lost or damaged due this problem.
Lets see the US come out with some new advances in tech with lower cost.