Is input impedance of an opamp independent from its input's frequency components?
If something has an infinite impedance then  any frequency cannot affect it however, it's never going to be infinite and as frequency rises the small amount of capacitance associated with the input will start to become significant even if the input resistance stays in the Giga ohm range.

The frequency won't affect the capacitance but the amplitude of the voltage may cause this capacitance to change slightly on some devices. See varactor diodes and miller capacitance changes with applied voltages.