Items from Viet Nam are not restricted. But they do not get favorable status either. The problem is the U.S. State Department. The importers have to jump through a LOT of hoops(some very expensive) that only one attempted to import. They got slapped with so many extra charges, fees and regulations, they went out of business. By the time someone could get the AIA guns imported, they would have to charge a 500% margin just to break even, and NOBODY would be willing to pay that much for one of their guns.
That is why you probably will not see them in the U.S. anytime soon.