no. i'm sure it's the browser, i know because i tested it.
BUT consider that the language of the GUI is not bound to the language requested for web pages.
so it's likely that your french Opera decided to request italian pages because of your italian system, but you can change this, and to say it all, you didn't even need to download a different version of Opera.
CTRL+F12 > general > language for web pages
as i change the option in Opera, the template is changing its language, with not modification of HFS files.