I by no means an expert on this topic, but here's my thought: The resistance is unique for a given electric device so it's value would remain constant. But because voltage and current are oscillating, the current passing through as well as the voltage drop would also oscillate. The only way to really alter the effective resistance is based on how you place them: either in series or parallel.
Impedance is the analog of resistance in an AC circuit. It is a constant value dependent upon resistance, inductive reactance and capacitive reactance.