“I have built a nuclear — a weapons system that nobody’s ever had in this country before. We have stuff that you haven’t even seen or heard about… what we have is incredible”

Perhaps, a U.S. hyperglide-hypersonic nuclear weapon system?

Or perhaps the U.S. president was revealing the W76-2, a new nuclear warhead deployed for the Trident D-5 submarine-launched ballistic missiles.  The revelation would not be ‘secret’. These so-called ‘usable’ low-yield tactical nukes are assessed widely as bringing more risk of misjudgment and a strategic, catastrophic nuclear exchange.

As reported previously:

The U.S. Navy currently fields 12 nuclear-powered ballistic missile submarines, each equipped with approximately 20 Trident D-5 submarine launched missiles. Each D-5 carries between four and five W-76 warheads each. The W-76 has an explosive yield of approximately 100 kilotons, or about six times the power of the bomb dropped on Hiroshima. With a range of 4,600 miles, a U.S. missile submarine parked off the coast of Canada could rain up to 80-100 warheads on western Russia.

Δ  https://twitter.com/AtomicAnalyst/status/1100439661456097282

Δ  https://www.ucsusa.org/resources/new-low-yield-submarine-based-nuclear-warhead

Δ  https://thediplomat.com/2020/02/us-adds-low-yield-nuclear-weapon-to-its-submarine-arsenal