Exactly, the big problem the US has is that once it runs through the existing stockpiles of ammunition it can't produce new ones at the rate they're being consumed. For example, from 2008 to present, Lockheed Martin was able to produce 800 missiles, around 50 a year. https://armyrecognition.com/news/army-news/2023/lockheed-martin-announces-delivery-of-800th-thaad-interceptor-missile-system

To counter the 180 missiles Iran reportedly launched, requiring up to 2 interceptors each, would have exhausted nearly HALF of all THAAD missiles ever produced. And that's assuming there are enough launchers to even fire that many interceptors at once. The US is completely unprepared for the scale of war it is provoking around the globe.