Yes indeed. Semantics. And if you were not aware of it before, let me tell you that in the law how things are defined matter a great deal. You chose to define the term "effectively own" to suit your own purposes of defending your claim about ownership once I pointed out that in fact there are such things as private mailboxes. That's exactly the kind of tactic lawyers do — looking for the definition that suits the case they wish to make, if the law doesn't already provide a specific definition. So congratulations, you are more like the lawyers that you say you hate than you perhaps realize. I told you that I was using the term in the more legal sense — to effectively own something would mean having pretty much the same bundle of legal rights that a real owner would have. Within our own definitions we each may be right. But so what? None of that helps the OP with his problem, does it?
I outlined before the practical impact for the OP of all of this. He can complain to the USPS about it, though for the reasons I stated earlier I doubt the USPS will care much about it. But it's free to complain to his local postmaster and maybe the local postmaster would feel like talking to the homeowner about it. If I were the OP I wouldn't hold my breath on that, though. That said, if I were in his shoes I'd at least take a shot at it. If the USPS doesn't care, then whether the OP has some legal recourse depends on additional facts that we don't have. But even if he does, the time and expense of pursuing that remedy might not be worth it. This probably will come down to negotiating whatever deal he can get with the homeowner. If you have a different take on what the OP can do, by all means please do share it.