Why is the U.S. negotiation with India over nuclear weapons critical to the long term (century long) defense of the United States?
Examine the facts on the ground. Call this neo-realism. Best India source confirms that India now possesses 30-40 nuclear weapons in position to use. The arsenal includes sea-based missiles (submarine launched) and mobile-based missiles. The warheads are based entirely on plutonium derived from breeder reactors built over the last forty years with Canadian and Indian involvement.
What India wants is the ability to manufacture at least 30 weapons per year entirely from plutonum from breeder reactors. This is why India does not want the new breeder reactors to be available to inspectors as commercial/civilian sites.
India does not want to rely upon the nuclear weapons umbrella of the United States.
There is a nuclear arms race on the South Asian continent. India has a no first use policy. Pakistan does not have a no first use policy. China is pell-mell to outgun India and the U.S. and Australia and Japan.