I've noticed that the Christmas incandescent lights that my mother brought at various countries for use during holidays (Mainly during Hanukkah), have power supplies with a 60hz rated frequency (Despite 230V rated voltage), and our mains frequency is 50hz. As the power supply is electronic, is this mismatch in frequency can damage the power supplies?

Filtering capacitors may be somewhat more stressed, but 1. i would not expect such capacitor to exist in a Christmas lights set, 2. even then damage is very unlikely

So i think there is no problem to use the 60Hz lights on 50Hz

Be advised however, that Christmas lights (both Incandescent and LED) are not intended to last very long. Regardless of the line frequency, the lifetime of most of them is limited to few Christmas seasons in total

Incandescent lights don't care what you feed them they will work from DC up to 1000 Hz with no change so long as they get there rated voltage they are happy, ohm's law still applies and there is no change for a purely resistive load when changing frequencies.. ( you could more then likely take them right up in to the Thz range but they might turn into little antennas ) But if they were any thing with an inductive or capacitive load like a HID light with a ballast or a motor, thing's change with the frequency...

And if they use a small power supply to change 230 volt to say 12 volts, most are built to work on both 50/60 Hz standards but are labeled for the country they are sold in to meet any regulator requirements...