I found a great "table" showing the STANDARD for voltage -- but also shows the variable....
PG&E (Pacific Gas and Electric) "Voltage Tolerance Boundary"
https://mafiadoc.com/voltage-toleran...2569eccb0.html
The USA standard called for is based -- Note that word "based" -- on 120V
But as delivered (called "SERVICE) it is allowed to vary from 114 - 126V (+/- 5%)
If you read the voltage rating on an electric motor --- you'll find "115V" -- and if it's 240V -- you'll see the nameplate state "230V"
And now you'll understand why there is so much CONFUSION over voltage. LOL