I remember reading an article a couple years ago that they used a Land Rover as an example of Mexicans bringing old vehicles over the border and selling them to unwitting Americans after they refurbished the vehicles...I remember one of the focal points had something to do with shotty welds on them...what a coincidence you'd bring this up....maybe the Mexicans never did weld them.
As it was the whole side of the car, right side, it would be very expensive to fix, all paint would need to come off, then weld, then repaint. I can not see anyone wanting to do that, including Mexicans out to make a quick profit. :-)
That was the whole point of contention, the Mexicans were just painting over that which was already wrong if we follow along the story you just told. If no one knew in the first place these were bad vehicles then authorities would just assume the Mexicans did the bad welds then try and disguise with a paint job.
They most probably did not know, the only way to check is with a chisel and hammer, and tap along the seam where the spot welds are, then it comes open easier than a can of peas.