All Nikkor lenses need to be imported from Japan by Nikon USA and sold through an authorized dealer for the USA warranty to be honored in the event of a need for service or repair. Amazon is authorized and you should have no problem. If you purchased this lens yourself overseas or through a non-authorized dealer, you wouldn't be covered.
I purchased the 14 - 24f/2.8 AF-S ED Nano G and was able to read 'made in Japan' on the lens. I saw this before trying the lens. Awesome lens. Nothing negative. Don't believe a gray market model would be available to even feel like this lens let alone perform.