Reformat localized date string to another locale

I have a String that is "Jueves 14 Junio 1990": it is a date formatted in the es_MX locale, I want to convert that into a new string with en_US as the locale.

This is my code:

let myString:String = "Jueves 14 Junio 1990"

let dateFormatter = NSDateFormatter()
dateFormatter.locale = NSLocale(localeIdentifier: "en_US")
dateFormatter.dateFormat = "EEEE dd MMMM yyyy"
let finalDate:NSDate = dateFormatter.dateFromString(myString)!
let finalString = dateFormatter.stringFromDate(date)

I was waiting that finalString resulted as Thursday 14 June 1990.

The problem here is that finalDate is nil.

Is my code wrong? How can I achieve this?