US troops DID serve as reinforcements to Brit, French units
Scott, as I've mentioned in previous posts, despite Pershing's and Wilson's supposedly strict policy for an all-American army on the WF, there were some instances of pragmatism on Black Jack's part when he authorised the detachment of smaller AEF formations to gain combat experience alongside seasoned British and French units, such as approx. 8 platoons of the 33rd (Prairie Div, Illinois NG) being attached to the AIF in July 1918 for the Battle of Hamel (very 1st time Australian and US troops fought side-by-side), the 27th (EMPIRE STATE, NY NG) and 30th (OLD HICKORY, NC NG) also being temporarily assigned to the British 4th Army in early 1918, and the entire 93rd (BLOODY HAND) (Colored) Div being given to the French army. According to THE UNKNOWN SOLDIERS by Barbeau and Henri (1974), which is all about the African-American experience in WWI, there was also a proposal to assign the 92nd BUFFALO Div when it 1st arrived in France to British command (palming off the unwanted black outfit), but this was rejected out of hand.