Actually, I was inquiring if a 115V AC 400HZ inverter source were supplying power to a 115V/5V AC 60 HZ transformer. Would saturation occur as well in this configuration?
For such a small transformer I guess It should be possible without problems.
For transformers with higher rating it would be neccessary to compare iron loss for both operating conditions. But you need the data sheet of the magnetic sheets used and the number of turns to do this. For larger transformer even increased eddy current losses in the windings would have to be considered.