In the UK, Nikon UK provide an extra years warranty on bodies, and body/lens combinations.
There is 30 days to register, and warranty service is only available through local repairers, not any Nikon repairer world wide.
It is common for an extended warranty to be administered by an extended warranty insurer - it definitely is in the UK.
If USA works similar the information needs to be on the insurers records at an early date.
In the UK when you get the extra years warranty the paper work comes with an offer to extend the warranty from 2 to 5 years - at what I consider an expensive price.
Somebody (the customer) pays for the extra warranty and controlling costs is increasingly critical in a recession. Nikon USA might have recently become stricter in requiring compliance with the offer terms.
Many problems turn out to be a lack of intimate knowledge of complex modern camera equipment.