The U.S. Africa Command statement says the airstrike occurred early Tuesday about 50 kilometers (31 miles) west of the capital.
Dozens of Kenyan security personnel have been killed in recent months in the remote lands near the border with Somalia, in raids by the al Shabaab Islamist militants from Somalia.
The strike comes after the USA urged its nonessential diplomatic personnel to evacuate Mogadishu after it warned of a potential threat.
The group lost its foothold in Mogadishu in 2011 but has continued its fight and still controls vast rural areas and is widely blamed for the country's worst ever bombing, which in October left 512 dead.More news: Watford's Troy Deeney admits VAR would have ruled out equaliser
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US forces will continue to use all authorized and appropriate measures to protect the United States, its partners and interests, and deny safe haven to terrorist groups.
The US carried out about 30 airstrikes against Al Shabaab in 2017, including a drone targeting the militant's training camp last month, which killed 100.
The Shabaab has been fighting to overthrow successive internationally backed governments in Mogadishu since 2007 and frequently deploys vehicle and truck bombs against military, government and civilian targets.
This is the first drone strike this year in Somalia. A Christmas Eve airstrike against Al-Shabaab killed 13 terrorists, U.S. Africa Command said.