Here's 2 questions that I do not know the answer to:
Is Nikon the only camera and lens manufacturer to have this type of policy regarding warranty repairs?
Does Nikon have this kind of policy in any other country?
The purpose of the policy, has nothing to do with the quality or specs of the lens. It is designed to protect Nikon's dealer network from being eroded by offshore sales, and by unauthorized sellers benefiting from Nikon authorized warranty service while undercutting Nikon's authorized dealer network. I think it is a sound policy, which you are free to ignore if you are willing to put up with the inconvenience of not getting your equipment warranty serviced in the US, or by Nikon's Melville and El Segundo service centers even if you are willing to pay.
Companies have the right to determine their distribution and service policies. You don't have a constitutional right to camera repair. If you find that commercial decision in their part to be not in your best interest, making the commercial decision to give your business to another camera company is entirely within your rights.