From The Times of Israel, "US Army scraps $1b. Iron Dome project, after Israel refuses to provide key codes":

The US Army said it was curbing its plans to adopt the Iron Dome missile defense system due to concerns about its compatibility with existing US technologies, scrapping its plans to buy two more batteries and explore long-term integration of the Israel-developed system.

A central problem was Israel's refusal to provide the US military with Iron Dome's source code, hampering the Americans' ability to integrate the system into their air defenses.

[…] The Army earmarked over $1 billion for the project to pluck select Iron Dome components and integrate them with US military's Integrated Battle Command System by 2023.

The Israeli Missile Defense Organization and the Army last August inked a deal for two Iron Dome batteries. Soon thereafter, according to sources, Army officials repeatedly requested Iron Dome "source code" — proprietary information detailing how the system works.

Israel supplied engineering information but ultimately declined to provide the source code the Army said it needed to integrate Iron Dome components with US systems.