Earlier quoted context omitted.
It’s not a common confusion at all though. No one would ever confuse Italian for English because they use the same script. It’s only “common” wrt Arabic script languages.
I think your familiarity with the Latin script is coloring your perceptions a bit, I'm an arab and when I was a child I used to classify French, Italian and all languages that use Latin letters as 'English'. Growing up is not what made me realize this is wrong, it's learning English. It's very easy to imagine the other way around.
These three have a lot of words in common. French-English share something like 30% of their respective vocabulary on top of an other 30% they both inherited from Latin. So, you were almost right!