Il nostro appartamento è stato allagato 2 settimane prima di trasferirci dagli Stati Uniti.

Looks like you got scammed! Have you viewed the apartment? You already paid some money?

FYI, you still have a valid rental contract and it’s not just an easy case of canceling it willy-nilly for your landlord. It is your landlord’s duty to provide you with living space during the renovation. How? Not your problem to figure, but rather your landlord’s. Your landlord also ought to be insured for that, and in turn then insurance can hold the previous tenants liable. You need to be very clear in communicating this to your landlord that you insist on keeping the rental contract and that you expect the same from them (assuming you actually do).