I think it was later than that - probably 1944 - possibly 43.
I think you're right there Mike, it was definitely towards the end of WWII. They manned the gun emplacements on the Great & Little Orme's and helped run the Coast Artillery School.
They also brought quite a few vehicles with them - American tanks were often seen parked just off the Conway Road.
I don't believe they ever manned the artillery school as it was only used by British Coastal Artillery regiments that were being trained in searchlights, gunnery and radio skills.
I once was told that they took over Lady Forester's (now St Dunstan's) and used it as a field hospital but this might just be heresay.
Oh, so what was the purpose of American troops being billeted to Llandudno then? They frequented a place named The Donut Dugout, which was an establishment in Vaughan Street, which catered to the US force.
Here is part of a biography of a nurse from US Army 297th General Hospital Unit:
" It seemed in no time at all after receiving our notification to join the 297th General Hospital that we found ourselves burdened with 40 pound field packs and struggling up the gang plank of the Queen Elizabeth on Memorial Day weekend of 1944 (date of embarkation, May 30, 1944). I would not describe this trip as exactly a pleasure cruise! We were packed in like sardines: 10,000 battle ready troops and 75 nurses! Despite tight security in rerouting our troop transport train from New Jersey and boarding ship after midnight as a large security secret, we sailed from New York Harbor at high noon on Memorial Day 1944 with all New York standing dockside on the bright clear sunny day to wave “goodbye” to our troop laden ship! (By now we were sure that all Germany knew we were on the way.)
Unfortunately, we hit stormy weather in the mid-Atlantic with gale winds as we neared the Irish Sea. It seemed like a sheer miracle when we safely arrived at Gourock, Scotland, hours before dawn broke through the mist on 6 June 1944. We waited on deck for hours in a cold light drizzle to be taken off the ship by tender and put ashore. We were all deeply grateful to the British Red Cross volunteers waiting for us dockside in the “wee” hours of the morning with sandwiches and hot coffee.
Soon after we disembarked, we boarded a train for our destination in Llandudno, North Wales where we would spend the next few days awaiting and assembling our medical supplies. It was at our Llandudno stop-off when we first learned of the Normandy invasion and [Operation Overlord]. Again, another long train ride across Wales and the cold grey English countryside to Stourbridge on the Severn River, our final destination in the midlands of England."
Obviously this doesn't explain the soldiers with tanks! However I believe that in the build up to D-Day, American and Canadian troops and equipment were shipped over to the UK in huge numbers and they had to dock ships on the West Coast from Liverpool to Scotland well away from interception by German Planes getting wind of the huge army gathering. Llandudno was probably being used as a stop off for a while before moving South.