When Cinderella Fought the Spanish Government by John Witiw.
"Titled Erase Una Vez, or Once Upon a Time, Spanish film company Estela Films attempted to tell the story of La Cenicienta, or Cinderella, as an animation the same year that Disney released theirs. For years, it was considered to be a lost film, but a black and white version of the original Cinefotocolor film has been uncovered and clips have been released on YouTube. Coincidentally, both films heavily used rotoscoping (the practice of drawing over live film) to produce life-like animation, as seen below."
Click through to the article to read more about how this film compared to the Disney, and how Disney's success put this film into obscurity.
"When it was released, it won a ‘Menzione d’honore’ in a Venetian Film Festival where it was said to be recognized as best children’s film. It was also deemed worthy of national interest. However, Disney’s success globally eclipsed the ambitious little picture. Even Spanish critics thought Disney’s version had better technical animation and it was unable to make up its budget of 5 million pesetas. The failure is believed to have killed Estela Films’ animation department, cancelling an upcoming film called Viaje Fantástico"
But there were even issues coming from the Spanish government at the time. I don't understand the particulars of the politics, but censorship from home also hurt the film's success.