Audiozenoligy
That is not true. If all they did was transmit 60Hz, then linear power supplies would not work. There is considerably energy above 60Hz.
The limitation in frequency response will be the transformer primarily.
In America all of the power grid is generated at 60 Hz. That included the 120 Volt line at your house to the ultra high voltages in the long distance transmission lines. But it all has to be at exactly 60 Hz or power gets wasted and bad things happen.
Are you mistaking Hz (cycles per second) for voltage? From the power plant voltages can be stepped up for transmission to thousands of volts (so you can use a smaller wire) but close to every house there is a step down transformer that converts it to 120 volts for home use. The only energy you get is 120 Volts at 60 Hz. That is what your components use and everything else should be considered noise.
Switching power transformers can be universal so you can plug them in to a 240 volt 50 Hz European power outlet and it still works. But it has nothing to do with the small amount of electrical interference at frequencies other than 50 Hz for Europe or 60 Hz in North America.
