Firefox recently changed my primary language on ALL WEBSITES from English to French. I've tried to reset default language to English using Options>Language but it doesn't make the change. I've refreshed Firefox. I've removed both French and English as primary language and then chosen English again. Nothing works. Thanks for assistance.
If the Firefox user interface (toolbars) is in the wrong language or if you want to change the current language then download Firefox in the language of your choice.
After all of the time spent on unsuccessful troubleshooting (THANKS ANYWAY) I decided enough was enough and so I unstilled FF and reinstalled a new US English version. GUESS WHAT--It launched in French Version.
I don't know why Google is displaying pages to you in French. Everything you have told us so far indicates that your Firefox is signaling to websites that you prefer U.S. English.
Are you able to switch your Google search results from French to English on Google's languages page: https://www.google.com/preferences#languages --