Some 15,000 minority Shia Turkmen in Amerli have been surrounded by Islamic State (IS) militants for two months.
The US also carried out air strikes on IS positions. The Iraqi army, Shia militias and Kurdish fighters have been struggling to break the siege.
Aircraft from the UK, Australia, France joined the US in the humanitarian aid drops, said Rear Admiral John Kirby.
Food, water, and medical supplies were delivered.
Rear Adm Kirby said operations would limited in scope and duration, as required to protect civilians trapped in Amerli.