human physiology - Why is the resting membrane potential of excitable tissue not affected by the extracellular sodium concentration?

I know that the resting membrane potential for excitable tissue (eg, nerve) is primarily determined by the electronegative difference between the inside and the outside of the membrane for potassium ions, as they are most permeate ion by far. And since the membrane is largely impermeable to sodium, it's diffusion potential is insignificant, as such it does not contribute much to the resting membrane potential. However, is it not correct to think that if the concentration of sodium ions in the extracellular fluid drops, outward diffusion of the positive potassium ions will increase, because the outside of the membrane is now less positive (more negative), subsequently making the diffusion potential of potassium and the resting membrane potential more on the negative side and further from the action potential threshold. I am asking this because my professor was mentioning factors that affect the resting membrane potential, and he mentioned that the ECF concentration of sodium has no effect on the resting membrane potential.