An allied URSS mean that Italy will probably side with the Axis instead of remain neutral, while Mussolini commerced with the URSS and basically built the Red Navy a formal alliance was out of the question for both pratical (both Italy and URSS wanted the same thing aka a lot of influence in the balkans), ideological (fascism gain power in Italy on a very anti-communist platform and the king will have never permitted such alliance and i don't even talk about the problem with the Pope) and personal (Benny ego was too big to even entertain the notion that he must share 2 place in the alliance with Stalin...he will have barely accepted that Germany was number one)