Having identified the source of the problem, I carried a portable AM radio over to my neighbor's house and explained the problem. We walked out the garage and switched the converter on/off and definitively identified the source of the problem. I provided him a list of filters that he could pick up at Western Radio that would filter the noise before it headed out to the transformer. End of problem. He just didn't know about the problem or means to resolve it.
As you see ‘things’ are manufactured and the FCC, agency tasked with preventing such interference, doesn’t care. If it kills AM radio then the deep state mission is advanced.