With the rampant U.S. propaganda against them and the supposed attack on the USS Maine, Spain was being portrayed very negatively on the world stage in the late 19th century. I'm sure Spain attempted to deny all of these charges but how did the rest of the world, Europe in particular, view Spain? Was the American propaganda successful in convincing not only the American people but other countries that the U.S. was in the right?
Interesting question. Not really helpful, but the answer is somewhere in the book European Perceptions of the Spanish-American War of 1898 by Hilton/Ickringill. I read it a long time ago and if I remember correctly, politicians and editors cared more about U.S. imperial ambitions than about the question if the war was justified. I remember that British newspapers showed sympathy for the Cubans, though.
A few quick notes on your assumptions: the explosion of the USS Maine was not assumed or cited to be the major reason for the war. As far as I know, there was no conscious American 'propaganda' abroad or intended for an international audience.