I’m gonna guess that what he’s attempting to refer to here is the Iron Dome system of Israeli fame.

We already have anti-ballistic missile systems:

• the Ground-Based Midcourse Defense system is exactly what it sounds like
• Aegis, Patriot, and THAAD are all short-range, terminal phase anti-ballistic-capable systems.

Also, to be clear, it would be a very bad idea for the US to pursue an expansion of the GMD system to be “impermeable” to a peer state, because not only would it be cripplingly expensive (even in the context of US military budgets), but it would also diminish the disincentive of doing a nuclear first strike (which would obviously lead directly to an intercontinental nuclear war), and you can guess who would want to do something like that.