The AA-12 is not a production piece it's a trophy design by Black Water International, designed by a gent named Jerry Baber. This weapon is not in mass production nor is it something issued to serving Black Water members.
The fact is the U.S Gov has been trying to create a fully automatic shotgun platform since the 1970's, this was due to the type of fighting seen in Vietnam and where the U.S army thought it would be filling it's combat rolls in the future.
In my opinion the fully automatic shotgun will never be common place, bulky limited range and a ammo hog this limits it's combat effectiveness.
Furthermore with AK-47's and M4's being the standard found in most engagements around the world the AA/12 would simply not be combat effective with it's limited range in most engagements.
As for USAS-12, what I stated above applies here surely, it's not a common weapon platform for the U.S Army nor the Marines.
In my opinion the era of Fully Auto combat shotguns has passed before it even arrived.
P.S: Is it just me or the picture of the USAS-12 have a Daewoo service manual, dont they make cars and electronics?! Next time I hear someone bad talk Daewoo's cars I'll tell them the guns they make are not half bad!
Now if someone could tell what type of Fully Automatic Shotgun is displayed below, would be nice. Personally never seen one like that.
And no, it's not a Franchi Spas-15