The America tax payer footed the bill for this boondoggle system. Like so may other projects before it, it's real purpose was to funnel money from America to Israel. The billions every year are apparently not enough so an extra two hundred million was approved by congress almost instantly after it was requested. Since this was the main purpose of Iron Dome. you can call it successful no matter how badly the system operates.
12 Iraqi troops, militiamen killed in multiple ISIS suicide attacks (AP)
from the article: Israel deploys Iron Dome missile defense system for first time