I don't know where it would be used here in North America
Several Caribbean nations use 50Hz power, mostly those which were/are colonies of the UK or other European countries, e.g. Barbados, Jamaica (120V), Guadeloupe, Martinique, St. Lucia, Dominica (220-240V).
The frequency will affect timing devices that are synchronized to the supply, as has already been mentioned, but there are other items which can be affected. The ballast in a fluorescent light fixture is an example. The inductive reactance is dependent upon the applied frewuency, so the current will be different when run on the "wrong" supply. Similar constraints apply to transformers: Although not a problem for small xfmrs in appliances, it can be significant for a big power xfmr (i.e. multi kVa).