At present only one unit American military unit wears a “sun helmet” – the Royal Guard of the Hawaii National Guard, a ceremonial unit of the Air National Guard. It essentially “re-enacts” the royal bodyguards of the Kingdom of Hawaii from the late 19th century.
The actual bodyguards disbanded when the monarch fell at the end of the 19th century, and the current Royal Guards were created 1962. It is made up of Hawaii residents who are Hawaii Air National Guardsman, and who are either full or part-Hawaiian ancestry. The unit serves at state functions and as for the state’s governor.