Nice find Peter,
Apart from the standard AM latrine in shot, what is interesting is the use of Studebaker 6x6 trucks.
The majority of these were supplied to the UK and USSR under Lend-Lease, very few were directly used by the US Army.
Close examination of the foremost truck shows a possible X-prefix to the serial number. This is usually seen on former British lend-lease vehicles transferred to the US Army, so would make sense.
The bumper code SOS-751-Q-TRK indicates a vehicle of the 751st Quartermaster Truck Company, Services of Supply.
This unit was stationed at Wylye at the time of the photo, moving to the depot at Kingham by September 1943.
The 751st was a "colored unit", so I'd suggest the majority of the personnel in the photo are American rather then Pioneer Corps as captioned, especially as they are wearing US uniforms.
All the best,