2 things: 1) These missiles are called "attack-ems" (ATACMs) which is just so American. 2) Even without ATACMs and THAAD interceptors, the US can do a lot of damage to Iran/Iraq/Yemen, but increasingly it will come at the cost of American lives. These systems are what give America its impunity.
CNBCU.S. has used 'virtually all' of its long-range precision missiles during Iran war: Reuters