From 2003 to 2011 Iran has been responsible for the majority of US casualties in Iraq. Following the decade long Iran/Iraq war Iran flooded their neighbor with cash, rockets and weapons technology. These proxy groups including both Sunni and Shia militias have allowed Iran to carry on a proxy war against the West and its Allies.
Iran supplied Shia militias in Iraq with the technology and materials to manufacture EFP’s of Explosively Formed Projectiles, the most lethal type of roadside bomb responsible for the death and mutilation of thousands of American Soldiers.
Only the US withdrawal from the region in 2011 slowed down the death count. Iran remains to this day the key destabilizing influence in the Middle East. Anti-Western, violent reprisal, doctrine remains the central focus of the Iranian regime.
Iran did not act alone, they were aided by a group of international banks that funneled money to Iran over a ten year period in stark violation of international sanctions that prohibited such transactions.