I sent my appeal letter and got another rejection.
It appears that Nissan does not understand the situation.
They seem to think I want this covered under a basic warranty claim.
They can deny the claim because I am beyond the mileage for a warranty claim. That is plain and simple. Further, talking to them on the phone they had an attitude and were very condescending. So much for great customer service.

What they don't seem to understand is that I am pointing out a flaw or defect in the parts. I have taken my X to a spring specialist in my area who told me this kind of failure should never have happened to a vehicle that is only five years old. Further, they agreed with me that since I have never been off-road and this still happened...they should not be claiming in their sales brochure that the Xterra features "rigid leaf springs" that can handle the toughest rocks when off-roading if it cannot even handle simple freeway driving without a failure.

I sent them complete specs of the small camper I tow about six times a year for camping...it weighs about half of the rated towing capacity of the Xterra which as you may know is 5,000 lbs.

Lucky for me, I also then appealed to my servicing Dealer, Luther Nissan of Inver Grove Heights, Minnesota. I have had all of my service done at this dealership and have been very happy with the services I have received there.
I appealed to them for help and they offered to do the repair at a very reduced cost and they apologized that Nissan was unable to help me. This is something I won't forget.

Lessons Learned:

Once you go past 100,000 miles, no auto manufacturer is going to care about your problems....apparently no matter what it is.

New vehicle sales brochures have inflated claims about the durability of their products and the parts on their vehicles. Best to review the websites where actual owners post their reviews.

Great customer service is not something to expect from Nissan corporate. There are plenty of other horror stories about them, mostly about about the Xterra (and other models) and the radiator problems.

While the dealer shop might be expensive, they know what they are doing and are fully trained. It pays to take the time to ask for help in these difficult situations. The worst that can happen is that they say no.

Nissan "Support" twitter site and web support are not actually supportive.
They don't take the time to fully listen and understand your story. I found it best to put it in writing. After I complained about the denial of my case they dropped me as a "friend".

The Xterra Owners Club is a great group of people.
Thanks for your support.