If an American HQ company at battalion level was similar to its WW1 British counterpart, then the company could include:
The Regimental Sergeant Major
Quartermasters
Cooks
Pioneers
Drivers
Signallers
Stretcher Bearers
Officers Batmen
Other possibles were shoemaker, armourer, orderly room clerk, padre.
The nominal strength of aBritsh battalion was 1007 in 1914. American infantry regiments had three battalions, which were slightly larger than the British battalions. This gave a nominal strength for an American regiment of 3832. Similar in size to a British brigade. In the British Army there were 4 battalions to a brigade (3 from early 1918 due to 'wastage')