Just some info on the USAS in 1918, both the USAS's 17th and 148th Aero Squadrons flew Sopwith Camels. Captain Elliot White Springs of the 148th scored 12 of his 16 victories flying Camels. It was not just an RAF fighter, and the US personnel did not just fly French aircraft. Also, many flew with the RAF, either as volunteers or as USAS personell on attached duty, and at least 4 became aces on the Se-5a.
Re the SPADs, im sure they will make it in before too long. Its too important of a type not to.