The hysteresis, loss, and nonlinearity of the strain and polarization response of an epitaxial PbZr0.55Ti0.45O3 film are experimentally investigated for non-switching AC excitation fields at a DC bias of 20 kV cm−1 in the 70 Hz to 5 kHz range. The measured strain is hysteretic and linear, whereas the polarization is hysteretic and highly nonlinear with excitation amplitude. Furthermore, compared to the case with zero bias, the effective piezoelectric coefficient that is extracted from the strain response is almost not changed for the investigated field range. In contrast, the loss tangent and nonlinearity of the polarization response are strongly reduced. The observations can not be explained by the Rayleigh model and its extensions, but are very well explained by the recently proposed polarization rotation model through addition of a non-zero bias field term to the model. This model describes the film properties as the result of the nonlinear rotation of the polarization vector within the unit-cell in response to the applied field, which is accompanied with viscous domain interaction. These results demonstrate that the polarization rotation model can describe the film response in a broad range of excitation frequencies and amplitudes, which far the applicable range of the Rayleigh model.