High voltage in the US is rare compared to the common inadequate CG wiring and low voltage.
In Mexico (this is the Mexico Forum) the CFE standard in many areas is 127 VAC. We often see the 127 or more - in some area I see 132 as the norm. Many variables whether you have high or low in Mexico. Can vary from one side of the RV park to the other. The device I suggest is for Mexico and the question asked I believe was about Mexico. A low voltage regulator could be useful in the US - but maybe not so much in Mexico.