Why can China with rated voltage of 220V be used normally under the voltage of 1 10V in the United States?

Suppose the voltage in the United States is 1 10V: although the internal use of switching power supply is not marked as wide voltage, it often has a wide working voltage because of the working principle of switching power supply. Portable DVD players and chargers are almost all switching power supplies, so they can be used normally, but this normal use is conditional, and it can be done in a short time, and problems will occur after a long time. Hair dryer is not a switching power supply, because the internal circuit will work, but the heat will be significantly reduced and the air volume will be much smaller.