The position was not cancelled. Tom Bossert had the position and resigned, and Rob Joyce assumed an acting position role from April 10, 2018 to May 31, 2018 (after which he returned to the NSA).

The position simply has not been filled properly, like hundreds of other positions in government that have traditionally been filled in the past 4 decades.

The position was cancelled by executive order. Politics are one thing, but the facts in this case are materially different from what you state here.