Step away from the voltage switch and turn around slowly. This should have been set correctly by the importer or dealer.
To save producing a different version of the amp with power transformers for each market, the manufacturers have opted to use a "universal" transformer which needs to be switched for the voltage available. You MUST leave this set to the "115" setting for the US. It would pay to check that you have the right value fuse for your voltage. Check in the amp's specifications.
Old "international model" Fenders had a rotary switch which allowed 110, 115, 120, 220, 230 and 240 volt settings.