You can use a 2nd order low pass filter made from an inductor (in series with the AC) and a capacitor to neutral. You will also need a resistor.
1 Henry and 10uF form a 2nd order low pass filter that will attenuate the higher order frequencies from the sq wave and make the output signal more sinusoidal in nature. It might work fine or it still might give your TV problems if it is particularly sensitive to harmonics.
The resistor is needed to keep the Q of the circuit low and prevent high ringing voltages.
Q = 1RLC−−√ = 3.16 using the values above.