| 10.2.2 the congiuntivo in irreal if clauses
A lot of people may believe that in an unreal if-clause English uses the simple past, you can even find that statement in some grammar books.
If I had money, I would buy a car.
But if you construct a similar sentence with to be
you realise that the simple past conjunctive is used.
If I were rich, I would buy a car.
not: If I was.....
It is the same in Italian. In an unreal if-clause, in other words in if-clauses where the realisation of the event / action described by the verb seems improbable, the imperfetto is used.