After looking at the original link you posted and the reference to North Africa, I looked a little deeper and it appears that I may have been premature with the 63rd Fighter Squadron reference.
The first link I posted in my previous post has a second squadron with the "UN" designator, the 84th Fighter Squadron under the 1st Fighter Group. I found very little information on the 84th Fighter Squadron so looked more under the 1st Fighter Group.
I had better luck there but found some conflicting information. In the Air Force Combat Units of World War II published by the Office of Air Force History,(available on line) it shows the following squadrons under the 1st Fighter Group;
There is no mention of the 84th Fighter Squadron under the 1st Fighter Group.
The 1st Fighter Group did serve in North Africa flying the P-38 as follows from the AF History sited above;
Moved to England, Tun-Jul 1942. Assigned to Eighth AF. Entered combat with P-38 aircraft on 28 Aug and flew a number of missions to France before being assigned to Twelfth AF for duty in the Mediterranean theater. Moved to North Africa, part of the ground echelon landing with the assault forces at Arzeu beach on 8 Nov 1942. The air echelon arrived a few days later and the group soon began operations, attacking enemy shipping, escorting bombers, flying strafing missions, and performing reconnaissance duties during the campaign for Tunisia.
In researching the individual squadrons, I finally found another P-38 with the "UN" squadron designator. The P-38 has the "UNQ" as its markings and is pictured in North Africa in 1943. The unit of assignment is the 27th Fighter Squadron which matches the Air Force History above for the 1st Fighter Group.