The system, which uses radar and interceptor missiles to combat incoming threats, has been in use since 2011.
The US Department of Defence has said the system will be used on a test basis, while it assesses options for the military’s long-term needs.
Israeli Prime Minister Benjamin Netanyahu has labelled the sale a “great achievement for the country”.
“This is another manifestation of the deepening of our steadfast alliance with the United States, and an expression of Israel’s rising status in the world,” his statement went on.
Iron Dome works by tracking incoming short-range projectiles by radar, then analyses data about the likely impact zone – before assessing whether to provide co-ordinates to a missile firing unit to intercept.
Israeli officials claim the missile system, which works in all weather and is transportable, has a success rate of up to 90%.
It is said to be able to provide city-sized protection against incoming aerial threats and has been utilised heavily to intercept missiles filed by Palestinian militants from the Gaza Strip.
The system took years to develop and is produced by Israel’s state-run defence firm Rafael Advanced Defence Systems.
The US has already heavily subsidised the system’s creation, and some of its components already come from American firms.
In a statement, Israel’s Military of Defence said the purchase was made because of the “immediate needs” of the US army.
US Army Colonel Patrick Seiber has said the system would be “assessed and experimented” with to protect deployed US personnel on a test basis only.
“While Iron Dome has been in operational use by the Israeli Air Force since 2011 and proven effective in combat, it should be noted that the US army will assess a variety of options for its long-term IFPC (Indirect Fire Protection Capability Increment) solution,” a statement released on Wednesday said.