I don't think this has anything to do with the Serie A or any other domestic association. The Super League is a mid-week tournament challenging the UCL, domestic leagues are pressed by UEFA to act like this new competition is actually damaging. TV revenues for domestic leagues are still in place, and in fact, the smaller teams could renegotiate to get more money out of the TV deal. The gap between the elite clubs and others will get bigger, yes, but that doesn't mean the smaller clubs are going bankrupt or even get hit financially, it's just a case where the big clubs will become richer.
The way I see it, and I could be wrong, Its a battle between the elite clubs and UEFA. League associations are threatened by UEFA to take a stand against it or otherwise risk getting no financial aid from UEFA and they have nothing to lose. Just oppose and see who wins at the end. Either way, 80-90% of their financial income is secured by TV rights for their domestic leagues not UEFA.