The ship was the Maersk Alabama.
It is operated by the Maersk Line... a US-based subsidary of the Danish company A.P. Moller-Maersk Group.
Maersk lines provides U.S. flag transportation, ship management and technical services to government and commercial customers.
U.S. Flag Transportation Service offers flexible and reliable end-to-end transport for any U.S. government cargo, from containers and military vehicles, to breakbulk and humanitarian food aid.
Maersk Line, Limited: Home
In order to get the US government contracts, the ship(s) to be used must be US-flagged and crewed by US-nationals.